Effects of increased free fatty acid availability on adipose tissue fatty acid storage in men

Fat Cell Size: Measurement Methods, Pathophysiological Origins, and Relationships With Metabolic Dysregulations

The obesity pandemic increasingly causes morbidity and mortality from type 2 diabetes, cardiovascular diseases and many other chronic diseases. Fat cell size (FCS) predicts numerous obesity-related complications such as lipid dysmetabolism, ectopic fat accumulation, insulin resistance, and cardiovascular disorders. Nevertheless, the scarcity of systematic literature reviews on this subject is compounded by the use of different methods by which FCS measurements are determined and reported. In this paper, we provide a systematic review of the current literature on the relationship between adipocyte hypertrophy and obesity-related glucose and lipid dysmetabolism, ectopic fat accumulation, and cardiovascular disorders. We also review the numerous mechanistic origins of adipocyte hypertrophy and its relationship with metabolic dysregulation, including changes in adipogenesis, cell senescence, collagen deposition, systemic inflammation, adipokine secretion, and energy balance. To quantify the effect of different FCS measurement methods, we performed statistical analyses across published data while controlling for body mass index, age, and sex.

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.

Exosomes and Obesity-Related Insulin Resistance

Exosomes are extracellular vesicles, delivering signal molecules from donor cells to recipient cells. The cargo of exosomes, including proteins, DNA and RNA, can target the recipient tissues and organs, which have an important role in disease development. Insulin resistance is a kind of pathological state, which is important in the pathogeneses of type 2 diabetes mellitus (T2DM), gestational diabetes mellitus and Alzheimer's disease. Furthermore, obesity is a kind of inducement of insulin resistance. In this review, we summarized recent research advances on exosomes and insulin resistance, especially focusing on obesity-related insulin resistance. These studies suggest that exosomes have great importance in the development of insulin resistance in obesity and have great potential for use in the diagnosis and therapy of insulin resistance.

Sex differences between Helicobacter pylori infection and cholesterol levels in an adult health checkup program

BACKGROUND

Helicobacter pylori (H pylori) infection is suggested to be a risk factor of metabolic syndrome (MS) and lipid abnormalities. The aim of this study was to investigate the influence of H pylori infection on MS and lipid abnormalities according to sex differences.

MATERIALS AND METHODS

We analyzed a total of 4551 adults who received health checkups from January 2016 to May 2017. We enrolled participants who did not have a history of hypertension, diabetes, hyperlipidemia, or cancer among those who underwent endoscopy with a rapid urease test.

RESULTS

We included a total of 1065 participants, and 663 patients (62.3%) were H pylori-positive. The H pylori infection rate was 59.3% (426/719) in males and 68.5% (237/346) in females. The mean level of total cholesterol (P = .003), low-density lipoprotein (LDL) cholesterol (P = .046), and triglycerides (P = .029) were statistically higher in H pylori-infected males. The mean level of high-density lipoprotein (HDL) cholesterol was statistically lower in H pylori-infected females (P = .032). Multivariate analysis showed that total cholesterol in males (odds ratio [OR], 1.007; 95% confidence interval [CI], 1.002-1.011) and HDL cholesterol in females (OR, 0.983; 95% CI, 0.968-0.998) were associated with active H pylori infection. The prevalence of MS was higher in both male and female H pylori-infected groups; however, there was no statistical significance.

CONCLUSIONS

H pylori infection is significantly related to increased total cholesterol in males and to decreased HDL cholesterol in females, which suggests that H pylori could affect lipid profiles and may be different by sex.

Gender Differences in the Pharmacological Actions of Pegylated Glucagon-Like Peptide-1 on Endothelial Progenitor Cells and Angiogenic Precursor Cells in a Combination of Metabolic Disorders and Lung Emphysema

In clinical practice, the metabolic syndrome (MetS) is often associated with chronic obstructive pulmonary disease (COPD). Although gender differences in MetS are well documented, little is known about sex-specific differences in the pathogenesis of COPD, especially when combined with MetS. Consequently, it is not clear whether the same treatment regime has comparable efficacy in men and women diagnosed with MetS and COPD. In the present study, using sodium glutamate, lipopolysaccharide, and cigarette smoke extract, we simulated lipid metabolism disorders, obesity, hyperglycemia, and pulmonary emphysema (comorbidity) in male and female C57BL/6 mice. We assessed the gender-specific impact of lipid metabolism disorders and pulmonary emphysema on angiogenic precursor cells (endothelial progenitor cells (EPC), pericytes, vascular smooth muscle cells, cells of the lumen of the nascent vessel), as well as the biological effects of pegylated glucagon-like peptide 1 (pegGLP-1) in this experimental paradigm. Simulation of MetS/COPD comorbidity caused an accumulation of EPC (CD45⁻CD31⁺CD34⁺), pericytes, and vascular smooth muscle cells in the lungs of female mice. In contrast, the number of cells involved in the angiogenesis decreased in the lungs of male animals. PegGLP-1 had a positive effect on lipids and area under the curve (AUC), obesity, and prevented the development of pulmonary emphysema. The severity of these effects was stronger in males than in females. Furthermore, PegGLP-1 stimulated regeneration of pulmonary endothelium. At the same time, PegGLP-1 administration caused a mobilization of EPC (CD45⁻CD31⁺CD34⁺) into the bloodstream in females and migration of precursors of angiogenesis and vascular smooth muscle cells to the lungs in male animals. Gender differences in stimulatory action of pegGLP-1 on CD31⁺ endothelial lung cells in vitro were not observed. Based on these findings, we postulated that the cellular mechanism of in vivo regeneration of lung epithelium was at least partly gender-specific. Thus, we concluded that a pegGLP-1-based treatment regime for metabolic disorder and COPD should be further developed primarily for male patients.

Association of serum total fatty acids with type 2 diabetes

BACKGROUND

Type 2 diabetes (T2D), a typical metabolic disease, is closely associated with serum free fatty acids. But the association between serum total fatty acids (TFAs, free fatty acids plus esterified fatty acids) and T2D has not been reported.

METHODS

Serum esterified fatty acids were hydrolyzed under alkaline conditions, and serum TFAs were extracted after acidizing. Fourteen of serum TFAs in 1,828 serum samples, including 543 controls, 655 prediabetes, and 630 T2D patients, were simultaneously quantified based on the calibration curves of 8 fatty acids using matrix-assisted laser desorption/ionization-Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR MS).

RESULTS

Correlation analysis revealed strong correlations among serum TFAs and ratios of the TFAs in T2D patients compared with controls or prediabetes both in males and females. Receiver operating characteristic analysis indicated that a panel including fasting plasma glucose, glycosylated hemoglobin type A1c, gamma-glutamyltransferase, triglyceride, C18:1, and C20:3, has a good capability to distinguish prediabetes from T2D, with the sensitivity of 87.0%, the specificity of 91.0%, and the area under curve (AUC) of 0.96.

CONCLUSIONS

In this study, rapid, absolute, and simultaneous quantification of serum TFAs was performed using MALDI-FTICR MS. C18:1 and C20:3 were significantly correlated with prediabetes and T2D.

Differential role of insulin resistance and β-cell function in the development of prediabetes and diabetes in middle-aged and elderly Chinese population

BACKGROUND

The prevalence of diabetes and prediabetes were estimated to be 10.9% and 35.7% in the Chinese adult population, respectively, and the middle-aged and elderly Chinese are at even higher risk of diabetes and prediabetes than younger population. With the increasing trend of aging in China, the burden of diabetes and related complications will be aggravated.

OBJECTIVES

Through comparing the indices of insulin resistance and β-cell function between subjects with different glucose metabolic status, to analyze the differential role of insulin resistance and β-cell function in the development of prediabetes and type 2 diabetes (T2DM) in the middle-aged and elderly Chinese population.

METHODS

In this cross-sectional study, we enrolled 512 participants aged 50 and over. The indices of insulin resistance (homoeostasis model assessment of insulin resistance (HOMA-IR) and adipose tissue insulin resistance (Adipo-IR), and indices of β-cell function [HOMA-β), fasting C-peptide to glucose ratio (FCPRI) and postprandial C-peptide to glucose ratio (PCPRI)] were calculated. Association of insulin resistance and β-cell function with prediabetes or T2DM were evaluated by multivariate logistic regression analysis, in which potential confounding factors were adjusted.

RESULTS

Of the 509 participants with complete information, 263 (51.7%) had normal glucose tolerance (NGT), 161 (31.6%) were in prediabetic status and 85 (16.7%) were overt T2DM. With the advancing of unfavorable glucose metabolism, the insulin resistance (HOMA-IR and Adipo-IR) and β-cell function (FCPRI, PCPRI) deteriorated (P _trend < 0.05 for all indices). We found that increase in insulin resistance expressed by Adipo-IR and HOMA-IR is associated with increased risk of prediabetes, whereas decrease in β-cell function expressed by HOMA-β and PCPRI is associated with increased risk of T2DM. We also demonstrated that Adipo-IR was more closely associated with developing prediabetes than HOMA-IR, and PCPRI was most closely related with developing T2DM among the indices of β-cell function used in this study.

CONCLUSIONS

Insulin resistance is the main determinant of developing prediabetes, whereas β-cell function is the main determinant of developing T2DM.

Sex differences in obesity, lipid metabolism, and inflammation-A role for the sex chromosomes?

BACKGROUND

Sex differences in obesity and related diseases are well established. Gonadal hormones are a major determinant of these sex differences. However, sex differences in body size and composition are evident prior to exposure to gonadal hormones, providing evidence for gonadal-independent contributions attributable to the XX or XY sex chromosome complement. Large-scale genetic studies have revealed male/female differences in the genetic architecture of adipose tissue amount and anatomical distribution. However, these studies have typically neglected the X and Y chromosomes.

SCOPE OF THE REVIEW

Here we discuss how the sex chromosome complement may influence obesity, lipid levels, and inflammation. Human sex chromosome anomalies such as Klinefelter syndrome (XXY), as well as mouse models with engineered alterations in sex chromosome complement, support an important role for sex chromosomes in obesity and metabolism. In particular, the Four Core Genotypes mouse model-consisting of XX mice with either ovaries or testes, and XY mice with either ovaries or testes-has revealed an effect of X chromosome dosage on adiposity, hyperlipidemia, and inflammation irrespective of male or female gonads. Mechanisms may include enhanced expression of genes that escape X chromosome inactivation.

MAJOR CONCLUSIONS

Although less well studied than effects of gonadal hormones, sex chromosomes exert independent and interactive effects on adiposity, lipid metabolism, and inflammation. In particular, the presence of two X chromosomes has been associated with increased adiposity and dyslipidemia in mouse models and in XXY men. The enhanced expression of genes that escape X chromosome inactivation may contribute, but more work is required.

Abnormal Myocardial Dietary Fatty Acid Metabolism and Diabetic Cardiomyopathy

Patients with diabetes are at very high risk of hospitalization and death from heart failure. Increased prevalence of coronary heart disease, hypertension, autonomic neuropathy, and kidney failure all play a role in this increased risk. However, cardiac metabolic abnormalities are now recognized to play a role in this increased risk. Increased reliance on fatty acids to produce energy might predispose the diabetic heart to oxidative stress and ischemic damage. Intramyocellular accumulation of toxic lipid metabolites leads to a number of cellular abnormalities that might also contribute to cardiac remodelling and cardiac dysfunction. However, fatty acid availability from circulation and from intracellular lipid droplets to fuel the heart is critical to maintain its function. Fatty acids delivery to the heart is very complex and includes plasma nonesterified fatty acid flux as well as triglyceride-rich lipoprotein-mediated transport. Although many studies have shown a cross-sectional association between enhanced fatty acid delivery to the heart and reduction in left ventricular function in subjects with prediabetes and diabetes, these mechanisms change very rapidly during type 2 diabetes treatment. The present review focuses on the role of fatty acids in cardiac function, with particular emphasis on the possible role of early abnormalities of dietary fatty acid metabolism in the development of diabetic cardiomyopathy.

Role of Adipose Tissue Insulin Resistance in the Natural History of Type 2 Diabetes: Results From the San Antonio Metabolism Study

In the transition from normal glucose tolerance (NGT) to type 2 diabetes mellitus (T2DM), the role of β-cell dysfunction and peripheral insulin resistance (IR) is well established. However, the impact of dysfunctional adipose tissue has not been fully elucidated. The aim of this study was to evaluate the role of resistance to the antilipolytic effect of insulin (adipose tissue IR [Adipo-IR]) in a large group of subjects with NGT, impaired glucose tolerance (IGT), and T2DM. Three hundred two subjects with varying glucose tolerance received an oral glucose tolerance test (OGTT) and euglycemic insulin clamp. We evaluated Adipo-IR (fasting and mean OGTT plasma free fatty acid [FFA] × insulin concentrations), peripheral IR (1/[Matsuda index] and (M/I)^-1 value), and β-cell function (calculated as the ratio of the increment in plasma insulin to glucose [OGTT/IR (ΔI/ΔG ÷ IR)]). Fasting Adipo-IR was increased twofold in obese subjects with NGT and IGT versus lean subjects with NGT (8.0 ± 1.1 and 9.2 ± 0.7 vs. 4.1 ± 0.3, respectively) and threefold in subjects with T2DM (11.9 ± 0.6; P < 0.001). Progressive decline in ΔI/ΔG ÷ IR was associated with a progressive impairment in FFA suppression during OGTT, whereas the rise in mean plasma glucose concentration only became manifest when subjects became overtly diabetic. The progressive decline in β-cell function that begins in individuals with NGT is associated with a progressive increase in FFA and fasting Adipo-IR.

Cellular Mechanisms Driving Sex Differences in Adipose Tissue Biology and Body Shape in Humans and Mouse Models

Sex differences in adipose tissue distribution and the metabolic, endocrine, and immune functions of different anatomical fat depots have been described, but they are incompletely documented in the literature. It is becoming increasingly clear that adipose depots serve distinct functions in males and females and have specific physiological roles. However, the mechanisms that regulate the size and function of specific adipose tissues in men and women remain poorly understood. New insights from mouse models have advanced our understanding of depot differences in adipose growth and remodeling via the proliferation and differentiation of adipose progenitors that can expand adipocyte number in the tissue or simply replace dysfunctional older and larger adipocytes. A limited ability of a depot to expand or remodel can lead to excessive adipocyte hypertrophy, which is often correlated with metabolic dysfunction. However, the relationship of adipocyte size and function varies by depot and sex. For example, femoral adipose tissues of premenopausal women appear to have a greater capacity for adipose expansion via hyperplasia and hypertrophy; although larger, these gluteal-femoral adipocytes remain insulin sensitive. The microenvironment of specific depots, including the composition of the extracellular matrix and cellular composition, as well as cell-autonomous genetic differences, influences sex- and depot-dependent metabolic and growth properties. Although there are some species differences, studies of the molecular and physiological determinants of sex differences in adipocyte growth and function in humans and rodents are both needed for understanding sex differences in health and disease.