Influence of increasing BMI on insulin sensitivity and secretion in normotolerant men and women of a wide age span

Heterogeneous response of estimated insulin sensitivity indices to metformin in young individuals with type 1 diabetes and different phenotypes

AIMS

This study aimed to investigate whether the response to adding metformin to insulin in young adults with type 1 diabetes (T1D) differs according to weight phenotype and insulin sensitivity index.

METHODS

A prospective pilot study was conducted over 26 weeks in which insulin plus metformin (2 g/day) was administered to 35 individuals, ranging from normal weight (NW) to overweight (OW) to obese (OB) T1D individuals, to correlate insulin sensitivity indices and other clinical variables.

RESULTS

At the end of the follow-up period, all groups showed an increase in the eGDR (NW: 7.37 vs 8.16, p = 0.002; OW: 7.28 vs 8.24, p < 0.001; OB: 6.33 vs 7.52 p < 0.001). KITT and SEARCH SCORE improved only in the OB group (2.15 vs 3.14, p < 0.001 and 5.26 vs 5.72, p = 0.007, respectively). Furthermore, HbA1c and BMI were significantly greater in the OB group (- 0.62%, p < 0.001; - 1.12 kg/m2, p = 0.031, respectively). Regression analysis revealed that the serum levels of triglycerides and uric acid were significantly (0.059, p = 0.013; 0.076, p = 0.001) associated with insulin sensitivity indices.

CONCLUSIONS

The study showed that eGDR improved independently of basal weight after metformin treatment. However, the KITT and SEARCH indices improved only in the obese group. Triglycerides and uric acid are associated with insulin sensitivity indices. These results highlight the heterogeneity of the mechanisms underlying insulin resistance and its response to metformin in individuals with T1D.

Association of a dietary pattern related to serum vitamin D levels with metabolic syndrome risk among Korean adults: based on the Korean national health and nutrition examination survey

PURPOSE

Vitamin D has a crucial role in our metabolic health. We aimed to examine associations of vitamin D status and its related dietary pattern (DP) with prevalent risk of metabolic syndrome (MetS) in 9,237 Korean adults aged 19-64 years based on the National Health and Nutrition Examination Survey.

METHODS

Vitamin D status was examined by serum 25-hydroxyvitamin D (25(OH)D). A vitamin D-related DP associated with 25(OH)D levels was derived using reduced rank regression (RRR). Associations of vitamin D status and its related DP with MetS prevalence were examined using multivariable logistic regression models adjusted for potential confounders.

RESULTS

Men with sufficient vitamin D status had a 44% lower risk of MetS prevalence (OR: 0.56; 95%CI: 0.36-0.87) compared to those with deficiency. A vitamin D-related DP derived using RRR was characterized by high intakes of vegetables, fish, fruits, and nuts and low intakes of eggs, oils, and mushrooms in this study population. Among men, the DP was significantly associated with a lower risk of MetS prevalence, showing a 12% (95%CI: 4-20%) reduction in risk for a one-unit increase in the DP score. However, there was no significant association among women.

CONCLUSION

The study's findings suggest that a sufficient vitamin D status and a related DP with high intakes of vegetables, fish, fruit, and nuts were associated with the risk of MetS, particularly in Korean male adults.

Hormonal regulation in diabetes: Special emphasis on sex hormones and metabolic traits

Diabetes constitutes a significant global public health challenge that is rapidly reaching epidemic proportions. Among the non-communicable diseases, the incidence of diabetes is rising at an alarming rate. The International Diabetes Federation has documented a 9.09% prevalence of diabetes among individuals aged between 20 and 79 years. The interplay of gonadal hormones and gender differences is critical in regulating insulin sensitivity and glucose tolerance, and this dynamic is particularly crucial because of the escalating incidence of diabetes. Variations in insulin sensitivity are observed across genders, levels of adiposity, and age groups. Both estrogen and testosterone are seen to influence glucose metabolism and insulin sensitivity. This chapter surveys the present knowledge of sex differences, sex hormones, and chromosomes on insulin imbalance and diabetes development. It further highlights the influence of metabolic traits in diabetes and changes in sex hormones during diabetic pregnancy. Notably, even stressful lifestyles have been acknowledged to induce hormonal imbalances. Furthermore, it discusses the potential of hormonal therapy to help stabilize sex hormones in diabetic individuals and focuses on the most recent research investigating the correlation between sex hormones and diabetes.

An in-silico modeling approach to separate exogenous and endogenous plasma insulin appearance, with application to inhaled insulin

The aim of this study was to develop a dynamic model-based approach to separately quantify the exogenous and endogenous contributions to total plasma insulin concentration and to apply it to assess the effects of inhaled-insulin administration on endogenous insulin secretion during a meal test. A three-step dynamic in-silico modeling approach was developed to estimate the two insulin contributions of total plasma insulin in a group of 21 healthy subjects who underwent two equivalent standardized meal tests on separate days, one of which preceded by inhalation of a Technosphere® Insulin dose (22U or 20U). In the 30-120 min test interval, the calculated endogenous insulin component showed a divergence in the time course between the test with and without inhaled insulin. Moreover, the supra-basal area-under-the-curve of endogenous insulin in the test with inhaled insulin was significantly lower than that in the test without (2.1 ± 1.7 × 104 pmol·min/L vs 4.2 ± 1.8 × 104 pmol·min/L, p < 0.01). The percentage of exogenous insulin reaching the plasma, relative to the inhaled dose, was 42 ± 21%. The proposed in-silico approach separates exogenous and endogenous insulin contributions to total plasma insulin, provides individual bioavailability estimates, and can be used to assess the effect of inhaled insulin on endogenous insulin secretion during a meal.

Consideration of sex as a biological variable in diabetes research across twenty years

BACKGROUND

Sex differences exist in the risk of developing type 1 and type 2 diabetes, and in the risk of developing diabetes-associated complications. Sex differences in glucose homeostasis, islet and β cell biology, and peripheral insulin sensitivity have also been reported. Yet, we lack detailed information on the mechanisms underlying these differences, preventing the development of sex-informed therapeutic strategies for persons living with diabetes. To chart a path toward greater inclusion of biological sex as a variable in diabetes research, we first need a detailed assessment of common practices in the field.

METHODS

We developed a scoring system to evaluate the inclusion of biological sex in manuscripts published in Diabetes, a journal published by the American Diabetes Association. We chose Diabetes as this journal focuses solely on diabetes and diabetes-related research, and includes manuscripts that use both clinical and biomedical approaches. We scored papers published across 3 years within a 20-year period (1999, 2009, 2019), a timeframe that spans the introduction of funding agency and journal policies designed to improve the consideration of biological sex as a variable.

RESULTS

Our analysis showed fewer than 15% of papers used sex-based analysis in even one figure across all study years, a trend that was reproduced across journal-defined categories of diabetes research (e.g., islet studies, signal transduction). Single-sex studies accounted for approximately 40% of all manuscripts, of which > 87% used male subjects only. While we observed a modest increase in the overall inclusion of sex as a biological variable during our study period, our data highlight significant opportunities for improvement in diabetes research practices. We also present data supporting a positive role for journal policies in promoting better consideration of biological sex in diabetes research.

CONCLUSIONS

Our analysis provides significant insight into common practices in diabetes research related to the consideration of biological sex as a variable. Based on our analysis we recommend ways that diabetes researchers can improve inclusion of biological sex as a variable. In the long term, improved practices will reveal sex-specific mechanisms underlying diabetes risk and complications, generating knowledge to enable the development of sex-informed prevention and treatment strategies.

Sex differences in the association between insulin resistance and non-fatal myocardial infarction across glycaemic states

BACKGROUND

Females are generally less prone to cardiovascular (CV) events than males, but this protection is trumped by diabetes. The mechanism behind the increased relative risk in females with diabetes is not fully understood. Insulin resistance (IR) is suggested to be a more important contributor to CV morbidity in females than in males. We aim to investigate differences in the association between IR indexes (Homeostatic Model Assessment of IR - HOMA-IR, visceral adiposity index - VAI, and triglycerides/high-density lipoprotein-cholesterol - TG/HDL-C index), and a first non-fatal myocardial infarction (MI) across different glycaemic states.

METHODS

IR indexes were calculated in a population with (n = 696) and without (n = 707) a first non-fatal MI, free from known diabetes. MI cases were investigated at least six weeks after the event. All participants were categorized by an oral glucose tolerance test as having normal glucose tolerance, impaired fasting glucose, impaired glucose tolerance, or newly diagnosed diabetes. Comparison of proportion of glycaemic states by sex was tested by chi-square test. The associations between sex, a first non-fatal MI, IR indexes, and traditional CV risk factors were analysed by multivariate logistic regression models. Continuous variables were logarithmically transformed.

RESULTS

Of the total population 19% were females and 81% males, out of whom 47% and 50% had a first non-fatal MI, respectively. Compared with males, females were older, less often smokers, with lower body mass index and higher total cholesterol and high-density lipoprotein cholesterol levels. The proportion of glycaemic states did not differ between the sexes (p = 0.06). Females were less insulin resistant than males, especially among cases and with normal glucose tolerance. In logistic regression models adjusted for major CV risk factors including sex, the associations between VAI and TG/HDL-C index and a first non-fatal MI remained significant only in females (odds ratios and 95% confidence intervals: 1.7, 1.0-2.9, and 1.9, 1.1-3.4 respectively).

CONCLUSIONS

These results support the assumption that IR indexes based on anthropometrics and lipid panel, i.e., VAI and TG/HDL-C, could be a better measure of IR and CV-predictor for non-fatal MI in females, even without glycaemic perturbations.

Transcriptome and secretome profiling of sensory neurons reveals sex differences in pathways relevant to insulin sensing and insulin secretion

Sensory neurons in the dorsal root ganglia (DRG) convey somatosensory and metabolic cues to the central nervous system and release substances from stimulated terminal endings in peripheral organs. Sex-biased variations driven by the sex chromosome complement (XX and XY) have been implicated in the sensory-islet crosstalk. However, the molecular underpinnings of these male-female differences are not known. Here, we aim to characterize the molecular repertoire and the secretome profile of the lower thoracic spinal sensory neurons and to identify molecules with sex-biased insulin sensing- and/or insulin secretion-modulating activity that are encoded independently of circulating gonadal sex hormones. We used transcriptomics and proteomics to uncover differentially expressed genes and secreted molecules in lower thoracic T5-12 DRG sensory neurons derived from sexually immature 3-week-old male and female C57BL/6J mice. Comparative transcriptome and proteome analyses revealed differential gene expression and protein secretion in DRG neurons in males and females. The transcriptome analysis identified, among others, higher insulin signaling/sensing capabilities in female DRG neurons; secretome screening uncovered several sex-specific candidate molecules with potential regulatory functions in pancreatic β cells. Together, these data suggest a putative role of sensory interoception of insulin in the DRG-islet crosstalk with implications in sensory feedback loops in the regulation of β-cell activity in a sex-biased manner. Finally, we provide a valuable resource of molecular and secretory targets that can be leveraged for understanding insulin interoception and insulin secretion and inform the development of novel studies/approaches to fathom the role of the sensory-islet axis in the regulation of energy balance in males and females.

Asian females without diabetes are protected from obesity-related dysregulation of glucose metabolism compared with males

OBJECTIVE

The impact of obesity on the risk for type 2 diabetes differs between males and females; however, the underlying reasons are unclear. This study aimed to investigate the effect of sex on obesity-driven changes in the mechanisms regulating glucose metabolism (insulin sensitivity and secretion) among Asian individuals without diabetes in Singapore.

METHODS

The study assessed glucose tolerance using oral glucose tolerance test, insulin-mediated glucose uptake using hyperinsulinemic-euglycemic clamp, acute insulin response using an intravenous glucose challenge, and insulin secretion rates in the fasting state and in response to glucose ingestion using mathematical modeling in 727 males and 952 females who had normal body weight (n = 602, BMI < 23 kg/m2 ), overweight (n = 662, 23 ≤ BMI < 27.5), or obesity (n = 415, BMI ≥ 27.5).

RESULTS

There were no sex differences among lean individuals. Obesity gradually worsened metabolic function, and the progressive adverse effects of obesity on insulin action and secretion were more pronounced in males than females, such that among participants with obesity, females had greater insulin sensitivity, lower insulin secretion, and lower fasting insulin concentration than males. The increase in waist to hip ratio with increasing BMI was more pronounced in males than females.

CONCLUSIONS

The female sex exerts a protective effect on obesity-driven dysregulation of glucose metabolism in Asian individuals without diabetes.

Sex Differences in Pancreatic β-Cell Physiology and Glucose Homeostasis in C57BL/6J Mice

The importance of sexual dimorphism has been highlighted in recent years since the National Institutes of Health's mandate on considering sex as a biological variable. Although recent studies have taken strides to study both sexes side by side, investigations into the normal physiological differences between males and females are limited. In this study, we aimed to characterized sex-dependent differences in glucose metabolism and pancreatic β-cell physiology in normal conditions using C57BL/6J mice, the most common mouse strain used in metabolic studies. Here, we report that female mice have improved glucose and insulin tolerance associated with lower nonfasted blood glucose and insulin levels compared with male mice at 3 and 6 months of age. Both male and female animals show β-cell mass expansion from embryonic day 17.5 to adulthood, and no sex differences were observed at embryonic day 17.5, newborn, 1 month, or 3 months of age. However, 6-month-old males displayed increased β-cell mass in response to insulin resistance compared with littermate females. Molecularly, we uncovered sexual dimorphic alterations in the protein levels of nutrient sensing proteins O-GlcNAc transferase and mTOR, as well as differences in glucose-stimulus coupling mechanisms that may underlie the differences in sexually dimorphic β-cell physiology observed in C57BL/6J mice.

Investigating family history of diabetes as a predictor of fasting insulin and fasting glucose activity in a sample of healthy weight adults

AIMS

Type 2 diabetes is a major public health problem for the global community. Having a family history of diabetes significantly increases risk for diabetes development and understanding how family history contributes to diabetes risk could lead to more effective prevention efforts for at-risk individuals. In a previous study, we showed family history of diabetes is a significant predictor of fasting insulin in healthy weight children. The present study aimed to use the National Health and Nutrition Examination Survey (NHANES 2017) to apply similar multiple regression models to a population of healthy weight adults to determine if family history is a significant predictor of fasting glucose and fasting insulin.

METHODS

Fasting glucose (mg/dL) and fasting insulin (pmol/L) were used as dependent variables in each model, respectively, with family history of diabetes as the independent variable. Covariates for each model included age, gender, race/ethnicity, waist circumference, and macronutrient intake.

RESULTS

The model significantly predicted the variance of fasting glucose [(F(11,364) = 34.80, p < 0.001, R² = 0.2342] and fasting insulin [F(11,343) = 17.58, p < 0.001, R² = 0.1162]. After adjusting for covariates, family history was a significant predicator of fasting glucose (p = 0.0193) as well as age, gender, non-Hispanic black ethnicity, waist circumference, and fat intake. Significant predictors of fasting insulin included gender and waist circumference, but not family history (p = 0.8264). In addition, fasting glucose was higher in individuals with a family history of diabetes (p = 0.033).

CONCLUSIONS

These results add to the understanding of how family history influences the biomarkers that contribute to diabetes development. Knowledge of how family history of diabetes relates to fasting insulin and fasting glucose activity in healthy weight individuals can be used to design personalized screening and early prevention strategies.

Sex differences in islet stress responses support female β cell resilience

OBJECTIVE

Pancreatic β cells play a key role in maintaining glucose homeostasis; dysfunction of this critical cell type causes type 2 diabetes (T2D). Emerging evidence points to sex differences in β cells, but few studies have examined male-female differences in β cell stress responses and resilience across multiple contexts, including diabetes. Here, we address the need for high-quality information on sex differences in β cell and islet gene expression and function using both human and rodent samples.

METHODS

In humans, we compared β cell gene expression and insulin secretion in donors with T2D to non-diabetic donors in both males and females. In mice, we generated a well-powered islet RNAseq dataset from 20-week-old male and female siblings with similar insulin sensitivity. Our unbiased gene expression analysis pointed to a sex difference in the endoplasmic reticulum (ER) stress response. Based on this analysis, we hypothesized female islets would be more resilient to ER stress than male islets. To test this, we subjected islets isolated from age-matched male and female mice to thapsigargin treatment and monitored protein synthesis, cell death, and β cell insulin production and secretion. Transcriptomic and proteomic analyses were used to characterize sex differences in islet responses to ER stress.

RESULTS

Our single-cell analysis of human β cells revealed sex-specific changes to gene expression and function in T2D, correlating with more robust insulin secretion in human islets isolated from female donors with T2D compared to male donors with T2D. In mice, RNA sequencing revealed differential enrichment of unfolded protein response pathway-associated genes, where female islets showed higher expression of genes linked with protein synthesis, folding, and processing. This differential expression was physiologically significant, as islets isolated from female mice were more resilient to ER stress induction with thapsigargin. Specifically, female islets showed a greater ability to maintain glucose-stimulated insulin production and secretion during ER stress compared with males.

CONCLUSIONS

Our data demonstrate sex differences in β cell gene expression in both humans and mice, and that female β cells show a greater ability to maintain glucose-stimulated insulin secretion across multiple physiological and pathological contexts.

The insulin signaling pathway a century after its discovery: Sexual dimorphism in insulin signaling

Since practically a century ago, the insulin pathway was discovered in both vertebrates and invertebrates, implying an evolutionarily ancient origin. After a century of research, it is now clear that the insulin signal transduction pathway is a critical, flexible and pleiotropic pathway, evolving into multiple anabolic functions besides glucose homeostasis. It regulates paramount aspects of organismal well-being like growth, longevity, intermediate metabolism, and reproduction. Part of this diversification has been attained by duplications and divergence of both ligands and receptors riding on a common general signal transduction system. One of the aspects that is strikingly different is its usage in reproduction, particularly in male versus female development and fertility within the same species. This review highlights sexual divergence in metabolism and reproductive tract differences, the occurrence of sexually "exaggerated" traits, and sex size differences that are due to the sexes' differential activity/response to the insulin signaling pathway.

Sex Differences in Glucose Homeostasis

Sexual dimorphism has been demonstrated to have an effect on various physiological functions. In this regard, researchers have investigated its impact on glucose homeostasis in both preclinical and clinical studies. Sex differences mainly arise from physiological factors such as sex hormones, body fat and muscle distribution, and sex chromosomes. The sexual dimorphism has also been studied in the context of diabetes. Reflecting the prevalence of the disease among the population, studies focusing on the sex difference in type 1 diabetes (T1D) are not common as the ones in type 2 diabetes (T2D). T1D is reported as the only major specific autoimmune disease that exhibits a male predominance. Clinical studies have demonstrated that impaired fasting glucose is more frequent in men whereas women more commonly exhibit impaired glucose tolerance. Understanding the sex difference in glucose homeostasis becomes more attractive when focusing on the findings that highlight sexual dimorphism on the efficacy or adverse effect profile of antidiabetic medications. Thus, in this chapter, we aimed to discuss the impact of sex on the glucose homeostasis both in health and in diabetes.

Biological underpinnings of sex differences in neurological disorders

The importance of sex differences in neurological disorders has been increasingly acknowledged in recent clinical and basic research studies, but the complex biology and genetics underlying sex-linked biological heterogeneity and its brain-to-body impact remained incompletely understood. Men and women differ substantially in their susceptibility to certain neurological diseases, in the severity of symptoms, prognosis as well as the nature and efficacy of their response to treatments. The detailed mechanisms underlying these differences, especially at the molecular level, are being addressed in many studies but leave a lot to be further revealed. Here, we provide an overview of recent advances in our understanding of how sex differences in the brain and brain-body signaling contribute to neurological disorders and further present some future prospects entailed in terms of diagnostics and therapeutics.

An epigenome-wide association study of insulin resistance in African Americans

Background

African Americans have a high risk for type 2 diabetes (T2D) and insulin resistance. Studies among other population groups have identified DNA methylation loci associated with insulin resistance, but data in African Americans are lacking. Using DNA methylation profiles of blood samples obtained from the Illumina Infinium® HumanMethylation450 BeadChip, we performed an epigenome-wide association study to identify DNA methylation loci associated with insulin resistance among 136 non-diabetic, unrelated African American men (mean age 41.6 years) from the Howard University Family Study.

Results

We identified three differentially methylated positions (DMPs) for homeostatic model assessment of insulin resistance (HOMA-IR) at 5% FDR. One DMP (cg14013695, HOXA5) is a known locus among Mexican Americans, while the other two DMPs are novel—cg00456326 (OSR1; beta = 0.027) and cg20259981 (ST18; beta = 0.010). Although the cg00456326 DMP is novel, the OSR1 gene has previously been found associated with both insulin resistance and T2D in Europeans. The genes HOXA5 and ST18 have been implicated in biological processes relevant to insulin resistance. Differential methylation at the significant HOXA5 and OSR1 DMPs is associated with differences in gene expression in the iMETHYL database. Analysis of differentially methylated regions (DMRs) did not identify any epigenome-wide DMRs for HOMA-IR. We tested transferability of HOMA-IR associated DMPs from five previous EWAS in Mexican Americans, Indian Asians, Europeans, and European ancestry Americans. Out of the 730 previously reported HOMA-IR DMPs, 47 (6.4%) were associated with HOMA-IR in this cohort of African Americans.

Conclusions

The findings from our study suggest substantial differences in DNA methylation patterns associated with insulin resistance across populations. Two of the DMPs we identified in African Americans have not been reported in other populations, and we found low transferability of HOMA-IR DMPs reported in other populations in African Americans. More work in African-ancestry populations is needed to confirm our findings as well as functional analyses to understand how such DNA methylation alterations contribute to T2D pathology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-022-01309-4.

Glucose Metabolism Derangements and Thyroid Nodules: Does Sex Matter?

(1) Background: Glucose metabolism derangements (GMD) and thyroid nodules (TNs) are the most frequent endocrine disorders, and their relationship is still controversial; little evidence is reported regarding sex differences. We aim to evaluate the association between GMDs and TNs according to sex and the sex differences in glucose metabolism and insulin sensitivity (IS). (2) Methods: We evaluated 342 patients (268 females and 74 males) at high GMD risk undergoing an oral glucose tolerance test and a thyroid ultrasound. (3) Results: The TN prevalence was 61% (n = 210), with no significant differences according to sex and GMD classes. The TN presence is significantly associated with age and impaired fasting glucose (IFG) in females. Males and females with normal fasting glucose (NFG) had a significantly lower OR of having TNs than females with IFG. IFG females had a significantly higher predicted probability of having TNs than NFG males and females but not IFG males. Impaired glucose tolerance/Type 2 diabetes mellitus (IGT/T2DM) is significantly associated with age and male sex, while IFG is associated with age. Females had significantly lower HOMA-index values than males. (4) Conclusions: No significant association between IGT/T2DM and TNs according to sex was found. IFG seems to play a role in TN development independently of sex. Further studies are needed to explore the relationship between TNs and GMD to identify subgroups with a higher TN risk.

How exposure to chronic stress contributes to the development of type 2 diabetes: A complexity science approach

Chronic stress contributes to the onset of type 2 diabetes (T2D), yet the underlying etiological mechanisms are not fully understood. Responses to stress are influenced by earlier experiences, sex, emotions and cognition, and involve a complex network of neurotransmitters and hormones, that affect multiple biological systems. In addition, the systems activated by stress can be altered by behavioral, metabolic and environmental factors. The impact of stress on metabolic health can thus be considered an emergent process, involving different types of interactions between multiple variables, that are driven by non-linear dynamics at different spatiotemporal scales. To obtain a more comprehensive picture of the links between chronic stress and T2D, we followed a complexity science approach to build a causal loop diagram (CLD) connecting the various mediators and processes involved in stress responses relevant for T2D pathogenesis. This CLD could help develop novel computational models and formulate new hypotheses regarding disease etiology.

Gender differences in cardiometabolic health and disease in a cross-sectional observational obesity study

Background

Beyond the degree of adiposity, the pattern of fat distribution has a profound influence on cardiometabolic risk. It is unclear if sex differences in body fat distribution can potentially explain any sex differences in the prevalence of the metabolic syndrome (MetS) and in individual cardiometabolic risk factors among obese men and women.

Methods

In this cross-sectional analysis, 432 persons from the ongoing Obesity Weight Reduction Study (n = 356 obese, ØBMI 41 ± 8 kg/m², and 76 non-obese, ØBMI 25 ± 3 kg/m²), were included. The relations of sex to MetS prevalence and selected cardiometabolic risk factors were assessed using univariate and multivariate adjusted regression models.

Results

In crude analyses, %fat mass and the fat mass/lean mass ratio were significantly higher in women than in men, regardless of increasing obesity categories, from normal weight to grade-3-obesity. In contrast, markers of abdominal obesity, such as waist circumference and waist-to-hip ratio were higher in men than in women, despite similar BMI. The prevalence of the MetS was higher in obese men than in women (67.6 vs. 45.0%, p < 0.0001), particularly in younger individuals < 40 years (72.5 vs. 36.8%, p < 0.0001), but “metabolically healthy obesity” (BMI ≥ 30, no other NCEP ATPIII MetS component) was more common in women than in men (15.6 vs. 4.1%, p < 0.0001). After adjusting for age, %body fat and height, sex differences were observed for HDL-cholesterol (p < 0.001), triglycerides (p < 0.001), fasting glucose (p = 0.002), insulin and HOMA-IR levels (p < 0.001), ALAT (p < 0.001), adiponectin (p < 0.001), and sE-selectin (p = 0.005). In contrast, crude sex differences in other variables, such as leptin levels (68 ± 4 in obese women vs. 33 ± 2 µg/L in men, p < 0.0001), disappeared after accounting for differences in %body fat (least-squares means of leptin: 52 ± 4 vs. 55 ± 6 µg /L, p = 0.740). A logistic regression model adjusting for age and lifestyle factors revealed a lower risk of having MetS for women as compared to men (OR = 0.38[0.22–0.60]). That risk estimate did not materially alter after adding BMI to the model. In contrast, no statistically significant association between sex and MetS prevalence was observed after adding waist circumference and adiponectin to the model (OR = 1.41[0.59–3.36]).

Conclusions

Different body fat distribution patterns, particularly abdominal adiposity, adiponectin, and related biomarkers, may contribute to sex differences in cardiometabolic risk factors and to the prevalence of the MetS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13293-022-00416-4.

Peripheral versus central insulin and leptin resistance: Role in metabolic disorders, cognition, and neuropsychiatric diseases

Insulin and leptin are classically regarded as peptide hormones that play key roles in metabolism. In actuality, they serve several functions in both the periphery and central nervous system (CNS). Likewise, insulin and leptin resistance can occur both peripherally and centrally. Metabolic disorders such as diabetes and obesity share several key features including insulin and leptin resistance. While the peripheral effects of these disorders are well-known (i.e. cardiovascular disease, hypertension, stroke, dyslipidemia, etc.), the CNS complications of leptin and insulin resistance have come into sharper focus. Both preclinical and clinical findings have indicated that insulin and leptin resistance are associated with cognitive deficits and neuropsychiatric diseases such as depression. Importantly, these studies also suggest that these deficits in neuroplasticity can be reversed by restoration of insulin and leptin sensitivity. In view of these observations, this review will describe, in detail, the peripheral and central functions of insulin and leptin and explain the role of insulin and leptin resistance in various metabolic disorders, cognition, and neuropsychiatric diseases.

Activation of gastrointestinal ileal brake response with dietary slowly digestible carbohydrates, with no observed effect on subjective appetite, in an acute randomized, double-blind, crossover trial

PURPOSE

To test the hypothesis that oral ingestion of slowly digestible carbohydrates (SDCs) that reach the ileum triggers the ileal brake as indicated by delayed gastric emptying, reduced glycemic response, and decreased subjective appetite.

METHODS

The study was a five-arm, randomized, double-blind, crossover trial with a 1-week washout period between treatments (n = 20; 9 females, 11 males). Five treatments consisted of three SDC ingredients [raw corn starch, isomaltooligosaccharide (IMO), sucromalt], and an IMO/sucromalt combination, shown in vitro to have slow and extended digestion profiles, and a rapidly digestible carbohydrate control (maltodextrin). Carbohydrates (26 g) were incorporated into yogurt [300 g total; carbohydrate (~ 77 g), fat (~ 0.2 g), and protein (~ 9 g)] with closely matched energy content (346 kcal) and viscosity (~ 30,000 cP). Outcomes were measured in a 4 h postprandial period.

RESULTS

Mean gastric half-emptying times were moderately though significantly increased for the raw corn starch and IMO treatments (P < 0.05), but they could be sub-divided into larger effect responder (n = 11) and non-responder groups (n = 9). Longer time for glycemic response to return to baseline was associated with increased gastric half-emptying time in an exploratory subset of data removing gastric half-emptying times > 3.5 h (P = 0.02). No significant differences in appetite ratings were observed.

CONCLUSION

SDCs caused slower gastric emptying rate through activation of the ileal brake, as closely matched semi-solid yogurts were used and only rate of carbohydrate digestion differed. Extending glycemic response through consumption of SDCs was associated with triggering the ileal brake.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03630445, August 2018, retrospectively registered.

Sex/Gender Differences in Obesity Prevalence, Comorbidities, and Treatment

PURPOSE OF REVIEW

Obesity is a heterogeneous condition, yet sex/gender is rarely considered in the prevention or clinical care of this disease. This review examined and evaluated recent literature regarding the influence of sex and gender on obesity prevalence, comorbidities, and treatment in adults.

RECENT FINDINGS

Obesity is more prevalent in women than men in most countries, but in some countries and population subgroups, this gap is more pronounced. Several obesity-related comorbidities, including type 2 diabetes and hypertension, demonstrate sex-specific pathways. Women, compared to men, are more likely to be diagnosed with obesity and seek and obtain all types of obesity treatment including behavioral, pharmacological, and bariatric surgery. Men tend to have greater absolute weight loss, but this difference is attenuated once accounting for baseline weight. Obesity is a multifactorial condition with complex interactions among sex/gender, sociocultural, environmental, and physiological factors. More sex/gender research is needed to investigate mechanisms underlying sex/gender differences in prevalence, comorbidities, and treatment, identify ways to increase men's interest and participation in obesity treatment, and examine differences in obesity prevalence and treatments for transgender and gender non-conforming individuals.

Insights into the physiology of C-peptide

Current knowledge suggests a complex role of C-peptide in human physiology, but its mechanism of action is only partially understood. The effects of C-peptide appear to be variable depending on the target tissue, physiological environment, its combination with other bioactive molecules such as insulin, or depending on its concentration. It is apparent that C-peptide has therapeutic potential for the treatment of vascular and nervous damage caused by type 1 or late type 2 diabetes mellitus. The question remains whether the effect is mediated by the receptor, the existence of which is still uncertain, or whether an alternative non-receptor-mediated mechanism is responsible. The Institute of Endocrinology in Prague has been paying much attention to the issue of C-peptide and its metabolic effect since the 1980s. The RIA methodology of human C-peptide determination was introduced here and transferred to commercial production. By long-term monitoring of C-peptide oGTT-derived indices, the Institute has contributed to elucidating the pathophysiology of glucose tolerance disorders. This review summarizes the current knowledge of C-peptide physiology and highlights the contributions of the Institute of Endocrinology to this issue.

Body surface area may explain sex differences in findings from the oral glucose tolerance test among subjects with normal glucose tolerance

BACKGROUND AND AIMS

Current guidelines on prediabetes and diabetes (T2D) recommend to regularly perform an oral glucose tolerance test (OGTT) on subjects at risk of T2D. However, it is not known why women tend to have relatively higher 2-h post-load plasma (2hPG) glucose concentrations during OGTT than men. The aim of the present study is to investigate if there are sex differences in fasting plasma glucose (FPG) and 2hPG concentrations in relation to body size in apparently healthy non-diabetic subjects with normal glucose tolerance. We hypothesized that sex differences in glucose tolerance are physiological and related to different body surface area (BSA) in men and women.

METHODS AND RESULTS

A 2-h 75 g OGTT was performed on 2010 subjects aged 45-70 years. Their BSA was calculated using the Mosteller formula. Men and women were separately divided into five BSA levels. Within the normal 2hPG range, women had higher mean 2hPG concentrations during the OGTT than men in all BSA levels estimated by sex-standardized BSA (p for linearity < 0.001). BSA adjusted for age, waist circumference, leisure-time physical activity, and smoking, showed an inverse association with 2hPG concentration in both sexes. Mean FPG concentrations were higher in men than in women.

CONCLUSIONS

Body size has a negative inverse association with 2hPG concentration in an OGTT even within a physiological plasma glucose range. This may cause underestimation of glucose disorders in individuals with larger BSA and overestimation in individuals with smaller BSA when using an OGTT.

Deconstructing the origins of sexual dimorphism in sensory modulation of pancreatic β cells

The regulation of glucose-stimulated insulin secretion and glucose excursion has a sensory component that operates in a sex-dependent manner.

OBJECTIVE

Here, we aim to dissect the basis of the sexually dimorphic interaction between sensory neurons and pancreatic β cells and its overall impact on insulin release and glucose homeostasis.

METHODS

We used viral retrograde tracing techniques, surgical and chemodenervation models, and primary cell-based co-culture systems to uncover the biology underlying sex differences in sensory modulation of pancreatic β-cell activity.

RESULTS

Retrograde transsynaptic labeling revealed a sex difference in the density of sensory innervation in the pancreas. The number of sensory neurons emanating from the dorsal root and nodose ganglia that project in the pancreas is higher in male than in female mice. Immunostaining and confocal laser scanning microscopy confirmed the higher abundance of peri-islet sensory axonal tracts in the male pancreas. Capsaicin-induced sensory chemodenervation concomitantly enhanced glucose-stimulated insulin secretion and glucose clearance in male mice. These metabolic benefits were blunted when mice were orchidectomized prior to the ablation of sensory nerves. Interestingly, orchidectomy also lowered the density of peri-islet sensory neurons. In female mice, capsaicin treatment did not affect glucose-induced insulin secretion nor glucose excursion and ovariectomy did not modify these outcomes. Interestingly, same- and opposite-sex sensory-islet co-culture paradigms unmasked the existence of potential gonadal hormone-independent mechanisms mediating the male-female difference in sensory modulation of islet β-cell activity.

CONCLUSION

Taken together, these data suggest that the sex-biased nature of the sensory control of islet β-cell activity is a result of a combination of neurodevelopmental inputs, sex hormone-dependent mechanisms and the potential action of somatic molecules encoded by the sex chromosome complement.

Recent Update on the Molecular Mechanisms of Gonadal Steroids Action in Adipose Tissue

The gonadal steroids, including androgens, estrogens and progestogens, are involved in the control of body fat distribution in humans. Nevertheless, not only the size and localization of the fat depots depend on the sex steroids levels, but they can also highly affect the functioning of adipose tissue. Namely, the gonadocorticoids can directly influence insulin signaling, lipid metabolism, fatty acid uptake and adipokine production. They may also alter energy balance and glucose homeostasis in adipocytes in an indirect way, e.g., by changing the expression level of aquaglyceroporins. This work presents the recent advances in understanding the molecular mechanism of how the gonadal steroids influence the functioning of adipose tissue leading to a set of detrimental metabolic consequences. Special attention is given here to highlighting the sexual dimorphism of adipocyte functioning in terms of health and disease. Particularly, we discuss the molecular background of metabolic disturbances occurring in consequence of hormonal imbalance which is characteristic of some common endocrinopathies such as the polycystic ovary syndrome. From this perspective, we highlight the potential drug targets and the active substances which can be used in personalized sex-specific management of metabolic diseases, in accord with the patient's hormonal status.

Gamma-aminobutyric acid attenuates insulin resistance in type 2 diabetic patients and reduces the risk of insulin resistance in their offspring

The role of gamma-aminobutyric acid (GABA) in attenuates insulin resistance (IR) in type 2 diabetic (T2D) patients and the reduction of the risk of IR in their offspring, and the function of GLUT4, IRS1 and Akt2 genes expression were investigated. T2D was induced by high fat diet and 35 mg/kg of streptozotocin. The male and female diabetic rats were then divided into three groups: CD, GABA, and insulin. NDC group received a normal diet. All the animals were studied for a six-month. Their offspring were just fed with normal diet for four months. Blood glucose was measured weekly in patients and their offspring. Intraperitoneal glucose tolerance test (IPGTT), urine volume, and water consumption in both patients and their offspring were performed monthly. The hyperinsulinemic euglycemic clamp in both patients and their offspring was done and blood sample collected to measure Hemoglobin A1c (HbA1c). IRS1, Akt and GLUT4 gene expressions in muscle were evaluated in all the groups. GABA or insulin therapy decreased blood glucose, IPGTT, and HbA1c in patients and their offspring compared to DC group. They also increased GIR in patients and their offspring. IRS1, Akt and GLUT4 gene expressions improved in both patients in comparison with DC group. GABA exerts beneficial effects on IRS1 and Akt gene expressions in GABA treated offspring. GABA therapy improved insulin resistance in diabetic patients by increasing the expression of GLUT4. It is also indirectly able to reduce insulin resistance in their offspring possibly through the increased gene expressions of IRS1 and Akt.

Prenatal Nicotine Exposure Induces Low Birthweight and Hyperinsulinemia in Male Rats

Smoking during pregnancy is one of the causes of low birthweight. Ingestion of nicotine during pregnancy has various metabolic impacts on the fetus and offspring. According to the developmental origins of health and disease theory, low birthweight is a risk factor for developing various non-communicable diseases, including diabetes. We hypothesized that when nicotine-induced low-birthweight rats, when exposed to a high-fat diet (HFD) after growth, are predisposed to glucose intolerance as a result of a mismatch between the eutrophic environment and small body size. Therefore, we investigated whether hyperinsulinemia was caused by exposure of nicotine-induced low-birthweight rats to HFD, including whether this phenomenon exhibited possible sex differences. The average birthweight and body weight at weaning day of offspring from nicotine-administered dams was lower than those of controls. The offspring from nicotine-administered dams did not show rapid fat accumulation after exposure to HFD, and weight and body fat ratio of these animals did not differ from those of the controls. Blood glucose levels did not differ between the groups, but insulin levels increased only in male HFD-exposed offspring from nicotine-administered dams. Similarly, only in HFD-exposed male from nicotine-administered dams showed decreases in the insulin receptor expression in the liver. We conclude that male rats subjected to prenatal nicotine exposure develop hyperinsulinemia when exposed to HFD after growth. Our results suggest that decreased expression of insulin receptors in the liver may be involved in the mechanism underlying hyperinsulinemia in low-birthweight offspring, a phenomenon that appeared to exhibit a sex-specific bias.

Relationship between Body Roundness Index and Risk of Type 2 Diabetes in Japanese Men and Women: A Reanalysis of a Cohort Study

PURPOSE

The purpose of this study was to investigate the association between body roundness index (BRI) and type 2 diabetes (T2DM) in each sex, explore the dose-response relationship between them, and evaluate the predictive value of BRI for T2DM.

MATERIALS AND METHODS

A retrospective cohort study was performed on 15,464 Japanese patients at the Murakami Memorial Hospital. Data on anthropometric indices and biochemical parameters were obtained. Multivariate Cox regression models were used to estimate the hazard ratios (HRs) of incident T2DM associated with BRI. Dose-response relationships were evaluated using a smoothing function analysis and the threshold effect. Receiver operating characteristic curves were used to evaluate and compare the predictive values of BRI, body mass index (BMI), and waist circumference (WC) for T2DM.

RESULTS

During a median 5.4-year follow-up period, 373 subjects were diagnosed with T2DM. After adjusting for age, alcohol intake, smoking status, fatty liver, systolic blood pressure, fasting plasma glucose, glycated hemoglobin, high-density lipoprotein cholesterol, triglycerides, and total cholesterol, the relationship between BRI and T2DM was linear in women (HR (95% CI) for BRI Z score = 1.48 (1.26,1.74)) and curvilinear in men (HR (95% CI) on the left and right of the inflection point = 0.70 (0.44, 1.10) and 1.46 (1.27, 1.67), respectively). Compared with BMI (area under the curve (AUC) = 0.684; p < 0.001) and WC (AUC = 0.700; p=0.007), BRI was the strongest predictor of T2DM in men (AUC = 0.715). Similarly, the AUC of BRI was larger than that of BMI (AUC = 0.757; p=0.966) and WC (AUC = 0.733; p=0.015) in women.

CONCLUSIONS

BRI was positively linearly associated with an elevated risk of incident T2DM in women. In men, the relationship between BRI and T2DM was J-shaped. BRI is an effective indicator of predicting T2DM. Its discriminatory power was higher than that of BMI and WC in both sexes.

Bone Marrow Metabolism Is Impaired in Insulin Resistance and Improves After Exercise Training

CONTEXT

Exercise training improves bone mineral density, but little is known about the effects of training on bone marrow (BM) metabolism. BM insulin sensitivity has been suggested to play an important role in bone health and whole-body insulin sensitivity.

OBJECTIVE

To study the effects of exercise training on BM metabolism.

DESIGN

Randomized controlled trial.

SETTING

Clinical research center.

PARTICIPANTS

Sedentary healthy (n = 28, 40-55 years, all males) and insulin resistant (IR) subjects (n = 26, 43-55 years, males/females 16/10).

INTERVENTION

Two weeks of sprint interval training or moderate-intensity continuous training.

MAIN OUTCOME MEASURES

We measured femoral, lumbar, and thoracic BM insulin-stimulated glucose uptake (GU) and fasting free fatty acid uptake (FFAU) using positron-emission tomography and bone turnover markers from plasma.

RESULTS

At baseline, GU was highest in lumbar, followed by thoracic, and lowest in femoral BM (all Ps < 0.0001). FFAU was higher in lumbar and thoracic than femoral BM (both Ps < 0.0001). BM FFAU and femoral BM GU were higher in healthy compared to IR men and in females compared to males (all Ps < 0.05). Training increased femoral BM GU similarly in all groups and decreased lumbar BM FFAU in males (all Ps < 0.05). Osteocalcin and PINP were lower in IR than healthy men and correlated positively with femoral BM GU and glycemic status (all Ps < 0.05).

CONCLUSIONS

BM metabolism differs regarding anatomical location. Short-term training improves BM GU and FFAU in healthy and IR subjects. Bone turnover rate is decreased in insulin resistance and associates positively with BM metabolism and glycemic control.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01344928.

Decrease in fasting insulin secretory function correlates with significant liver fibrosis in Japanese non-alcoholic fatty liver disease patients

Background and Aim

Non‐alcoholic fatty liver disease (NAFLD) is typically associated with metabolic syndrome and diabetes, and insulin resistance is involved in its pathogenesis. However, the relationship between insulin secretion and NAFLD is unclear. We aimed to characterize the relationship between fasting insulin secretory function (ISF), evaluated using the homeostatic model assessment‐beta cell function (HOMA‐β) and the severity of fibrosis during NAFLD.

Methods

A‐β was calculated in 188 patients with biopsy‐confirmed NAFLD, and the correlations between Log HOMA‐β and clinical parameters, including hepatic fibrosis, were calculated.

Results

Log HOMA‐β was significantly lower in NAFLD patients with significant fibrosis (stages 2–4) than in those in the early stages (stages 0–1) (median [interquartile range]) (2.1 [1.9–2.4] vs 2.0 [1.8–2.2], P = 0.04). The prevalence of significant fibrosis decreased with increasing Log HOMA‐β: it was 59.2% in participants with low ISF (Log HOMA‐β < 1.85), 43.6% in those with intermediate ISF (1.85 ≤ Log HOMA‐β < 2.25), and 68.0% in those with high ISF (Log HOMA‐β ≥ 2.25). Patients with lower Log HOMA‐β had lower current body mass index (BMI), BMI at 20 years of age, and peak lifetime BMI than patients with intermediate or high Log HOMA‐β.

Conclusions

Fasting ISF decreased alongside the development of liver fibrosis in NAFLD, suggesting that an impaired β cell function has a characteristic finding of significant liver fibrosis in relatively nonobese Japanese patients.

Sex differences in metabolic regulation and diabetes susceptibility

Gender and biological sex impact the pathogenesis of numerous diseases, including metabolic disorders such as diabetes. In most parts of the world, diabetes is more prevalent in men than in women, especially in middle-aged populations. In line with this, considering almost all animal models, males are more likely to develop obesity, insulin resistance and hyperglycaemia than females in response to nutritional challenges. As summarised in this review, it is now obvious that many aspects of energy balance and glucose metabolism are regulated differently in males and females and influence their predisposition to type 2 diabetes. During their reproductive life, women exhibit specificities in energy partitioning as compared with men, with carbohydrate and lipid utilisation as fuel sources that favour energy storage in subcutaneous adipose tissues and preserve them from visceral and ectopic fat accumulation. Insulin sensitivity is higher in women, who are also characterised by higher capacities for insulin secretion and incretin responses than men; although, these sex advantages all disappear when glucose tolerance deteriorates towards diabetes. Clinical and experimental observations evidence the protective actions of endogenous oestrogens, mainly through oestrogen receptor α activation in various tissues, including the brain, the liver, skeletal muscle, adipose tissue and pancreatic beta cells. However, beside sex steroids, underlying mechanisms need to be further investigated, especially the role of sex chromosomes, fetal/neonatal programming and epigenetic modifications. On the path to precision medicine, further deciphering sex-specific traits in energy balance and glucose homeostasis is indeed a priority topic to optimise individual approaches in type 2 diabetes prevention and treatment.

Quantity not composition of dietary fats represents the dominant contributor to experimental obesity: Relevance to human pathophysiology

Plant fats are low in saturated fats but high in unsaturated fats compared to animal fats, and are supposedly less obesogenic. This study compared the obesogenic effects of plant and animal derived fatty diets in Wistar rats. Rats of each gender were divided into three dietary (standard chow (SC), high fat diet rich in animal fat (HFDaf) and a high fat diet rich in plant fat (HFDpf)) groups of ten each and fed for 17 weeks. Anthropometric, Adiposity and nutritive variables were assessed using standard methods. Comparing HFDpf to HFDaf: Abdominal circumference (AC),initial feed intaken (IFI), final feed intake(FFI), final body weight (FBW), white adipose tissue (WAT) were increased but brown adipose tissue (BAT) decreased in male rats fed with HFDpf; also, there were increased body length, IFI, FFI but decreased AC, FBW, BAT in female rats fed with HFDpf. Comparing male to female rats: Thoracic circumference, IFI, FFI, energy intake were increased while Adiposity index decreased across diet groups in male rats; the AC, FBW increased while WAT, BAT decreased in HFDpf fed group, also, BAT was increased but AC, FBW decreased in HFDaf fed group in male rats. Palatability and high feed efficiency of consumed diets were more associated with obesogenic risk than just the level of saturation. Therefore, Obesogenic effects of fatty diets in both genders is more dependent on the quantity (amount) of fatty diet consumed than the dietary fat composition alone.

Postprandial glycemic response in a non-diabetic adult population: the effect of nutrients is different between men and women

Background

There is a growing interest in the pathopysiological consequences of postprandial hyperglycemia. It is well known that in diabetic patients 2 h plasma glucose is a better risk predictor for coronary heart disease than fasting plasma glucose. Data on the glycemic response in healthy people are scarce.

Objective

To evaluate the effect of macronutrients (carbohydrates, fats, and proteins) and fiber on postprandial glycemic response in an observational study of a non-diabetic adult population.

Design

Cross-sectional study. 150 non-diabetic adults performed continuous glucose monitoring for 6 days. During this period they recorded food and beverage intake. The participants were instructed not to make changes in their usual diet and physical exercise.

Variables analyzed included clinical parameters (age, sex, body weight, height, body mass index, blood pressure, and waist measurement), meal composition (calories, carbohydrates, fats, proteins, and fiber) and glycemic postprandial responses separated by sexes.

The study period was defined from the start of dinner to 6 h later.

Results

A total of 148 (51% women) subjects completed all study procedures. Dinner intake was higher in males than in females (824 vs 531 kcal). Macronutrient distribution was similar in both sexes. No significant differences were found in fiber intake between men and women (5.5 g vs 4.5 g).

In both sexes, the higher intake of carbohydrates corresponded to a significantly higher glycemic response (p = 0.0001 in women, p = 0.022 in men). Moreover, in women, as fat intake was higher, a flattening of the postprandial glycemic curve was observed (p = 0.003). With respect to fiber, a significantly lower glycemic response was observed in the group of women whose fiber intake at dinner was higher (p = 0.034).

Conclusions

Continuous glucose monitoring provides important information about glucose levels after meals. In this study, the postprandial glycemic response in women was different from that of men, and carbohydrates were the main determinant of elevated postprandial glucose levels.

Association between Salivary Fructosamine, Plasma Glycated Hemoglobin, and Plasma Glucose Levels among Type II Diabetes Mellitus and Nondiabetic Individuals-A Cross-sectional Study

OBJECTIVE

The study was aimed to determine the association between salivary fructosamine and plasma glycated hemoglobin, plasma fasting and postprandial glucose levels among patients suffering from type II diabetes mellitus and nondiabetic healthy individuals.

MATERIALS AND METHODS

The cross-sectional study was conducted in a hospital setting. A total of 100 participants were included, with 50 participants in each group-group I (patients with type II diabetes mellitus) and group II (nondiabetic healthy individuals). Blood and saliva samples were collected to estimate the levels of the blood and salivary parameters. Depending upon the normality, appropriate tests were used-t-test and Mann-Whitney U test were used for continuous data. Pearson chi-square test and Fisher's exact test were used for discrete data. To test for any positive association between salivary and blood parameters, simple linear regression was carried out.

RESULTS

The study results showed that group I had significantly higher levels of salivary fructosamine when compared to group II (p < 0.001). In groups I and II a significant positive association was observed between salivary fructosamine and plasma glycated hemoglobin (group I, r-value 0.893; group II, r-value 0.307).

CONCLUSION

The overall study results showed that salivary fructosamine levels were significantly higher in patients with diabetes when compared to nondiabetic individuals. Also, positive correlation was observed between salivary fructosamine, plasma fasting, plasma postprandial, and plasma glycated hemoglobin among both the groups.

[Consumption of red and processed meat, insulin resistance, and diabetes in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)Consumo de carnes rojas y de carne procesada, resistencia a la insulina y diabetes en el estudio longitudinal de salud del adulto (ELSA-Brasil)]

Objetivo.

Investigar a associação entre consumo de carne vermelha e processada e a ocorrência de novos casos de resistência insulínica (RI) e diabetes mellitus (DM) em participantes do Estudo Longitudinal de Saúde do Adulto (ELSA-Brasil).

Métodos.

Estudo de coorte com 15 105 servidores públicos (idade: 35 a 74 anos). Dados bioquímicos, antropométricos, socioeconômicos e de estilo de vida foram coletados na linha de base (2008–2010) e na segunda onda (2012–2014). O consumo de carnes (g/dia) foi estimado por questionário de frequência alimentar. Para categorizar baixo, médio e alto consumo as variáveis independentes foram divididas em tercis. DM foi diagnosticado como glicemia de jejum ≥ 126 mg/dL, glicose pós-sobrecarga ≥ 200 mg/dL ou hemoglobina glicada ≥ 6,5. RI foi determinada pelo índice HOMA-IR com pontos de corte construídos a partir do percentil 75 da amostra.

Resultados.

Homens e participantes com menor renda e escolaridade relataram maior consumo de carne vermelha e processada. Maior consumo de carne processada (último tercil, > 27,1 g/dia) associou-se a novos casos de RI em homens (OR = 1,68; IC95%: 1,31 a 2,16) e mulheres (OR = 1,23; IC95%: 1,00 a 1,52). Alto consumo de carne vermelha aumentou em 40% (IC95%: 1,04 a 1,96) a chance de novos casos de DM em homens.

Conclusões.

O consumo elevado de carne vermelha e processada teve impacto negativo na saúde dos participantes. O consumo moderado de carnes pode ser recomendado para a população em geral e para prevenção do DM.

Sex-based differences in hepatic and skeletal muscle triglyceride storage and metabolism 1

Women and men store lipid differently within the body with men storing more fat in the android region and women storing more fat in the gynoid region. Fat is predominately stored in adipose tissue as triacylglycerides (TG); however, TG are also stored in other tissues including the liver and skeletal muscle. Excess hepatic TG storage, defined as a TG concentration >5% of liver weight and known as nonalcoholic fatty liver disease (NAFLD), is related to the metabolic syndrome. Similarly, elevated skeletal muscle TG, termed intramyocellular lipids (IMCL), are related to insulin resistance in obesity and type II diabetes. Men store more hepatic TG than women and, unsurprisingly, NAFLD is more prevalent in men than women. Women store more IMCL than men, yet type II diabetes risk is not greater, which is likely due to the manner in which women store TG within muscle. Sex-based differences in TG storage between men and women are underpinned by differences in messenger RNA expression, protein content, and enzyme activities of skeletal muscle and hepatic lipid metabolic pathways. Furthermore, women have a greater reliance on lipid during exercise because of upregulation of lipid oxidative pathways. The purpose of this review is to discuss the role of sex in mediating lipid storage and metabolism within skeletal muscle and the liver at rest and during exercise and its relationship with metabolic disease.

Sex Differences in Glucose and Fatty Acid Metabolism in Asians Who Are Nonobese

CONTEXT

The prevalence of diabetes is increasing throughout Asia, even in the absence of obesity, and is lower in women than in men. The underlying mechanisms are not well understood.

OBJECTIVE

To evaluate the sex differences in glucose and fatty acid metabolism in Asians who are nonobese.

DESIGN

Cross-sectional study.

SETTING

Clinical Nutrition Research Centre, Singapore.

PARTICIPANTS

Healthy Asian men (n = 32; body mass index, 21.8 ± 1.5 kg/m2; age, 42 ± 14 years) and women (n = 28; body mass index, 21.4 ± 2.0 kg/m2; age, 41 ± 13 years).

MAIN OUTCOME MEASURES

Insulin sensitivity (insulin-mediated glucose uptake normalized for steady-state insulin; hyperinsulinemic-euglycemic clamp), postprandial glucose, insulin and fatty acid concentrations, insulin secretion (mixed meal tolerance test with mathematical modeling), insulin clearance, body composition and fat distribution (dual-energy X-ray absorptiometry, MRI, and spectroscopy), cardiorespiratory fitness (maximal oxygen uptake; graded exercise test), and handgrip strength (dynamometry).

RESULTS

Women had more total body fat but less visceral fat than men; liver and muscle lipid contents were not different. Maximal oxygen uptake and handgrip strength were lower in women than men. The postprandial glucose concentrations were ~8% lower, the insulin-mediated glucose uptake was ~16% greater, and the meal-induced suppression of fatty acid concentrations was significantly greater in women than in men (P < 0.05 for all). However, muscle insulin sensitivity was not different between the sexes. No differences were found in postprandial insulin secretion and clearance rates; however, the steady-state insulin clearance was ~17% lower in women.

CONCLUSIONS

Asian women who are nonobese are more insulin-sensitive than men at the level of adipose tissue but not skeletal muscle. Therefore, sex differences in glucose tolerance are likely the result of sexual dimorphism in hepatic insulin action.

Sex- and age-related differences of metabolic parameters in impaired glucose metabolism and type 2 diabetes compared to normal glucose tolerance

AIMS

This study analysed potential sex differences in glucose metabolism of European subjects with different degrees of glucose tolerance impairment.

METHODS

Subjects with impaired glucose metabolism, IGM (n = 735), or type 2 diabetes, T2DM (n = 415), were compared to subjects with normal glucose tolerance, NGT (n = 422), with similar BMI. For both males (M) and females (F), 50 years threshold was used for estimation of menopausal/andropausal state. Subjects underwent 75-g OGTT for measurements of insulin sensitivity (OGIS), beta-cell function (insulinogenic index, IGI_C), and overall metabolic condition, disposition index (DI).

RESULTS

In IGM, OGIS did not change with age in both sexes, whereas marked reduction of IGI_C was seen in F (p = 0.0003). In T2DM, again OGIS did not change with age, but M ≥ 50 yrs had reduced IGI_C and DI (p < 0.002) compared to M < 50 yrs.

CONCLUSIONS

IGM did not reveal relevant changes of insulin resistance with age, but early phase insulin release deteriorated, with higher change in women. T2DM men featured age-related deterioration of glucose metabolism. In women, sex advantage seen in NGT vanished in T2DM, since glucose metabolism was overall not different than in men, both young and elderly.

A Calcium-Deficient Diet in Dams during Gestation Increases Insulin Resistance in Male Offspring

Calcium (Ca) plays an important role in the pathogenesis of insulin resistance syndrome. Osteocalcin (OC), a bone formation biomarker, acts directly on β-cells and increases insulin secretion. We determined the effects of Ca deficiency during pregnancy and/or lactation on insulin resistance in offspring. Female Wistar rats consumed either a Ca-deficient or control diet ad libitum from three weeks preconception to 21 days postparturition. Pups were allowed to nurse their original mothers until weaning. The offspring were fed a control diet beginning at weaning and were killed on day 180. Serum carboxylated OC (Gla-OC) and undercarboxylated OC (Glu-OC), insulin and adipokines in offspring were measured. In males, mean levels of insulin, glucose, and HOMA-IR were higher in the Ca-deficient group than in the control group. In addition, ionized Ca (iCa) was inversely associated with serum Glu-OC and adiponectin in males. In females, mean levels of Glu-OC and Gla-OC in the Ca-deficient group were higher than in the control group. In all offspring, serum leptin levels were correlated with serum insulin levels, and inversely correlated with iCa. In conclusion, maternal Ca restriction during pregnancy and/or lactation influences postnatal offspring Ca metabolism and insulin resistance in a sex-specific manner.

Effect of body mass index on diabetogenesis factors at a fixed fasting plasma glucose level

Aim

The present study evaluated the relative influence of body mass index (BMI) on insulin resistance (IR), first-phase insulin secretion (FPIS), second-phase insulin secretion (SPIS), and glucose effectiveness (GE) at a fixed fasting plasma glucose level in an older ethnic Chinese population.

Methods

In total, 265 individuals aged 60 years with a fasting plasma glucose level of 5.56 mmol/L were enrolled. Participants had BMIs of 20.0–34.2 kg/m². IR, FPIS, SPIS, and GE were estimated using our previously developed equations. Pearson correlation analysis was conducted to assess the correlations between the four diabetogenesis factors and BMI. A general linear model was used to determine the differences in the percentage of change among the four factor slopes against BMI.

Results

Significant correlations were observed between BMI and FPIS, SPIS, IR, and GE in both women and men, which were higher than those reported previously. In men, BMI had the most profound effect on SPIS, followed by IR, FPIS, and GE, whereas in women, the order was slightly different: IR, followed by FPIS, SPIS, and GE. Significant differences were observed among all these slopes, except for the slopes between FPIS and SPIS in women (p = 0.856) and IR and FPIS in men (p = 0.258).

Conclusions

The contribution of obesity to all diabetes factors, except GE, was higher than that reported previously. BMI had the most profound effect on insulin secretion in men and on IR in women in this 60-year-old cohort, suggesting that lifestyle modifications for obesity reduction in women remain the most important method for improving glucose metabolism and preventing future type 2 diabetes mellitus.

Altered intragenic DNA methylation of HOOK2 gene in adipose tissue from individuals with obesity and type 2 diabetes

Aims/Hypothesis

Failure in glucose response to insulin is a common pathology associated with obesity. In this study, we analyzed the genome wide DNA methylation profile of visceral adipose tissue (VAT) samples in a population of individuals with obesity and assessed whether differential methylation profiles are associated with the presence of type 2 diabetes (T2D).

Methods

More than 485,000 CpG genome sites from VAT samples from women with obesity undergoing gastric bypass (n = 18), and classified as suffering from type 2 diabetes (T2D) or not (no type 2 diabetes, NT2D), were analyzed using DNA methylation arrays.

Results

We found significant differential methylation between T2D and NT2D samples in 24 CpGs that map with sixteen genes, one of which, HOOK2, demonstrated a significant correlation between differentially hypermethylated regions on the gene body and the presence of type 2 diabetes. This was validated by pyrosequencing in a population of 91 samples from both males and females with obesity. Furthermore, when these results were analyzed by gender, female T2D samples were found hypermethylated at the cg04657146-region and the cg 11738485-region of HOOK2 gene, whilst, interestingly, male samples were found hypomethylated in this latter region.

Conclusion

The differential methylation profile of the HOOK2 gene in individuals with T2D and obesity might be related to the attendant T2D, but further studies are required to identify the potential role of HOOK2 gene in T2D disease. The finding of gender differences in T2D methylation of HOOK2 also warrants further investigation.

A Calcium-Deficient Diet in Rat Dams during Gestation Decreases HOMA-β% in 3 Generations of Offspring

BACKGROUND

Prenatal malnutrition can affect the phenotype of offspring by altering epigenetic regulation. Calcium (Ca) plays an important role in the pathogenesis of insulin resistance syndrome.

AIMS

We hypothesized that a Ca-deficient diet during pregnancy would alter insulin resistance and secretion in more than 1 generation of offspring.

METHODS

Female Wistar rats consumed either a Ca-deficient or a control diet ad libitum from 3 weeks before conception to 21 days after parturition and were mated with control males. Randomly selected F1 and F2 females were mated with males of each generation on postnatal day 70. The F1 and F2 dams were fed a control diet ad libitum during pregnancy and lactation. All offspring were fed a control diet starting at the time of weaning and were sacrificed on day 180.

RESULTS

HOMA-β% decreased in F1 through F3, and levels in F2 and F3 males and females were significantly lower than in controls. The mean levels of insulin and HOMA-IR were higher in F1 males but lower in F3 males than in control males. The HOMA-IR did not differ between any of the female offspring and controls.

CONCLUSIONS

Maternal Ca restriction during pregnancy and/or lactation influences insulin secretion in 3 generations of offspring.

Insulin resistance and beta-cell dysfunction in people with prediabetes according to criteria based on glycemia and glycosylated hemoglobin

Impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) are well-known conditions of risk for diabetes. Recently, 1h-hyperglycemia (1h-HG), i.e., glycemia > 8.6 mmol/L, has been suggested as further condition of diabetes risk. Moreover, in 2010 the American Diabetes Association included the measurement of glycosylated hemoglobin (HbA1c) among the criteria of diabetes risk (5.7-6.4%). Aim of this study was investigating all these different conditions of diabetes risk, with specific focus on possible insulin sensitivity and beta-cell function changes, when 1h-HG, and further HbA1c-prediabetes, are added to the already deeply studied condition of IFG/IGT. In this study, we retrospectively analysed 744 participants that underwent 2h-OGTT and HbA1c measurement. Participants were stratified into groups: (i) normal glucose tolerance, NGT (n=178); (ii) IFG and/or IGT (n=88); (iii) IFG/IGT plus 1h-HG (n=342); (iv) IFG/IGT plus 1h-HG plus HbA1c-prediabetes (n=136). We calculated several indices of insulin sensitivity and beta-cell function, as well as an index considering both aspects (disposition index). We found that progressing from group (i) to group (iv) both insulin sensitivity and beta-cell function tended to further deteriorate; the parameter providing more evidence was the disposition index (p<0.008 in any group comparison). In conclusion, for appropriate assessment of the level of diabetes risk (especially in people already known to be at high risk), it may be convenient to measure all the indicated parameters, that is, glycemia at fasting, at one hour and two hours during OGTT, and glycosylated hemoglobin.

Sex and Gender Differences in Risk, Pathophysiology and Complications of Type 2 Diabetes Mellitus

The steep rise of type 2 diabetes mellitus (T2DM) and associated complications go along with mounting evidence of clinically important sex and gender differences. T2DM is more frequently diagnosed at lower age and body mass index in men; however, the most prominent risk factor, which is obesity, is more common in women. Generally, large sex-ratio differences across countries are observed. Diversities in biology, culture, lifestyle, environment, and socioeconomic status impact differences between males and females in predisposition, development, and clinical presentation. Genetic effects and epigenetic mechanisms, nutritional factors and sedentary lifestyle affect risk and complications differently in both sexes. Furthermore, sex hormones have a great impact on energy metabolism, body composition, vascular function, and inflammatory responses. Thus, endocrine imbalances relate to unfavorable cardiometabolic traits, observable in women with androgen excess or men with hypogonadism. Both biological and psychosocial factors are responsible for sex and gender differences in diabetes risk and outcome. Overall, psychosocial stress appears to have greater impact on women rather than on men. In addition, women have greater increases of cardiovascular risk, myocardial infarction, and stroke mortality than men, compared with nondiabetic subjects. However, when dialysis therapy is initiated, mortality is comparable in both males and females. Diabetes appears to attenuate the protective effect of the female sex in the development of cardiac diseases and nephropathy. Endocrine and behavioral factors are involved in gender inequalities and affect the outcome. More research regarding sex-dimorphic pathophysiological mechanisms of T2DM and its complications could contribute to more personalized diabetes care in the future and would thus promote more awareness in terms of sex- and gender-specific risk factors.

Strong evidence of sexual dimorphic effect of adiposity excess on insulin sensitivity

AIMS

Our aims were to investigate in several large samples, with a wide range of adiposity, whether: (1) the effect of BMI on insulin sensitivity is different between sexes; (2) also waist circumference plays a sex-specific role on insulin sensitivity; and (3) serum adiponectin and resistin are mediators of such sex-dimorphic effect.

METHODS

Samples used were: Gargano study 1 (GS1), GS2 and Catania study (CS) comprising 3274 individuals. Adiponectin and resistin were measured by ELISA. Associations between variables were tested by linear models.

RESULTS

In all samples, relationship between BMI and HOMAIR was steeper in males than in females (BMI-by-sex interaction p = 0.04-0.0007). No interaction was observed on serum adiponectin and resistin (p = 0.40-059), which are therefore unlikely to mediate the sex-dimorphic effect of BMI on insulin resistance. Relationship between waist circumference and HOMAIR was similar between sexes in GS1 and GS2 but not in CS (waist-by-sex interaction p = 0.01), comprising much heavier individuals. This suggests that a sex-dimorphic effect of abdominal adiposity on insulin resistance is observable only in the context of high BMI.

CONCLUSIONS

Our findings represent a proof of concept that BMI and insulin sensitivity are associated in a sex-specific manner. This may explain why females are protected from diabetes and cardiovascular disease, compared to males of similar BMI.

Does epigenetic dysregulation of pancreatic islets contribute to impaired insulin secretion and type 2 diabetes?

β cell dysfunction is central to the development and progression of type 2 diabetes (T2D). T2D develops when β cells are not able to compensate for the increasing demand for insulin caused by insulin resistance. Epigenetic modifications play an important role in establishing and maintaining β cell identity and function in physiological conditions. On the other hand, epigenetic dysregulation can cause a loss of β cell identity, which is characterized by reduced expression of genes that are important for β cell function, ectopic expression of genes that are not supposed to be expressed in β cells, and loss of genetic imprinting. Consequently, this may lead to β cell dysfunction and impaired insulin secretion. Risk factors that can cause epigenetic dysregulation include parental obesity, an adverse intrauterine environment, hyperglycemia, lipotoxicity, aging, physical inactivity, and mitochondrial dysfunction. These risk factors can affect the epigenome at different time points throughout the lifetime of an individual and even before an individual is conceived. The plasticity of the epigenome enables it to change in response to environmental factors such as diet and exercise, and also makes the epigenome a good target for epigenetic drugs that may be used to enhance insulin secretion and potentially treat diabetes.

Gender-based differences in glycaemic control and hypoglycaemia prevalence in patients with type 2 diabetes: results from patient-level pooled data of six randomized controlled trials

AIMS

To determine the impact of gender on glycaemic control and hypoglycaemia in insulin-naïve patients with type 2 diabetes (T2DM).

METHODS

Data were pooled from six randomized clinical trials of insulin glargine or NPH insulin in insulin-naïve, inadequately controlled patients. Female [n = 1251; mean glycated haemoglobin (HbA1c) level 8.99%, age 56.91 years, diabetes duration 9.84 years] and male patients (n = 1349; mean HbA1c 8.9%, age 57.47 years, diabetes duration 10.13 years) were started on and treated with insulin glargine or NPH insulin for 24-36 weeks. HbA1c and fasting blood glucose levels, percent achieving HbA1c target of <7% and insulin dose change were recorded.

RESULTS

For both men and women, HbA1c levels were significantly reduced over time (p < 0.001); a significantly greater HbA1c reduction was observed in men than in women (-1.36 vs. -1.22; p = 0.002). Significantly fewer women achieved target HbA1c of <7% (p < 0.001). At the study end, women had a significantly higher insulin dose/kg than men (0.47 vs. 0.42 U/kg; p < 0.001). The incidence rates of severe and severe nocturnal hypoglycaemia were significantly higher in women (3.28% vs. 1.85%; p < 0.05 and 2.24% vs. 0.59%; p < 0.001, respectively). Women were more likely to experience severe hypoglycaemia [odds ratio (OR) 1.80; 95% confidence interval (CI) 1.08, 3.00; p = 0.02] and severe nocturnal hypoglycaemia (OR: 3.80; 95% CI 1.72, 8.42; p = 0.001).

CONCLUSIONS

These observations confirm studies that found a smaller improvement in HbA1c and greater hypoglycaemia in women during insulin treatment. Physicians should be aware of the need to determine and closely monitor dosing, particularly in women, to optimize the balance between glycaemic control and hypoglycaemia risk.

Sex differences in the genome-wide DNA methylation pattern and impact on gene expression, microRNA levels and insulin secretion in human pancreatic islets

Background

Epigenetic factors regulate tissue-specific expression and X-chromosome inactivation. Previous studies have identified epigenetic differences between sexes in some human tissues. However, it is unclear whether epigenetic modifications contribute to sex-specific differences in insulin secretion and metabolism. Here, we investigate the impact of sex on the genome-wide DNA methylation pattern in human pancreatic islets from 53 males and 34 females, and relate the methylome to changes in expression and insulin secretion.

Results

Glucose-stimulated insulin secretion is higher in female versus male islets. Genome-wide DNA methylation data in human islets clusters based on sex. While the chromosome-wide DNA methylation level on the X-chromosome is higher in female versus male islets, the autosomes do not display a global methylation difference between sexes. Methylation of 8,140 individual X-chromosome sites and 470 autosomal sites shows sex-specific differences in human islets. These include sites in/near AR, DUSP9, HNF4A, BCL11A and CDKN2B. 61 X-chromosome genes and 18 autosomal genes display sex-specific differences in both DNA methylation and expression. These include NKAP, SPESP1 and APLN, which exhibited lower expression in females. Functional analyses demonstrate that methylation of NKAP and SPESP1 promoters in vitro suppresses their transcriptional activity. Silencing of Nkap or Apln in clonal beta-cells results in increased insulin secretion. Differential methylation between sexes is associated with altered levels of microRNAs miR-660 and miR-532 and related target genes.

Conclusions

Chromosome-wide and gene-specific sex differences in DNA methylation associate with altered expression and insulin secretion in human islets. Our data demonstrate that epigenetics contribute to sex-specific metabolic phenotypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-014-0522-z) contains supplementary material, which is available to authorized users.