The contribution of intraabdominal fat to gender differences in hepatic lipase activity and low/high density lipoprotein heterogeneity

Exploring the prognostic value of the novel nutritional index for in-hospital mortality in acute coronary syndrome: a sex-specific analysis

Background

Emerging evidence suggests that nutritional status plays a pivotal role in determining the prognosis of patients with acute coronary syndrome (ACS). This study aimed to investigate the relationship between a novel nutritional index, Triglycerides × Total Cholesterol × Body Weight Index (TCBI), and short-term prognosis in patients with ACS.

Methods

A retrospective study was conducted using data from 5,277 ACS patients admitted to intensive care units of 208 United States hospitals in the eICU Collaborative Research Database (eICU-CRD) in 2014 and 2015. Patients were divided into three groups based on TCBI tertiles: Group 1 (< 1017.97), Group 2 (1017.97-2069.02), and Group 3 (> 2069.02).

Results

Multivariate logistic regression analysis showed that after adjusting for 17 confounding variables, higher TCBI had significantly lower in-hospital mortality [Tertile 3 vs Tertile 1: OR (95% CI): 0.67 (0.48, 0.94), p = 0.019]. This relationship was significant in the male subgroup but not in the female subgroup. The association between TCBI and in-hospital mortality was more pronounced in male patients and those with blood pressure > 140 mmHg. Subgroup analysis revealed a significant interaction between sex and the predictive value of TCBI (p for interaction < 0.05).

Conclusion

Higher TCBI was independently associated with decreased in-hospital mortality in ACS patients, particularly in male patients. TCBI, as a novel nutritional index, may serve as a practical tool for risk stratification and personalized management of ACS patients.

Chinese Visceral Adipose Index is Associated with Arterial Stiffness in Type 2 Diabetes Patients: A Cross-Sectional Study

Purpose

The purpose of this study is to investigate the association between Chinese Visceral Adipose Index(CVAI) and brachial-ankle pulse wave velocity (baPWV) in type 2 diabetes (T2D) patients, in order to provide scientific evidence for the prevention and treatment of macrovascular complications in T2D.

Patients and Methods

This research adopts the cross-sectional study design. Anthropometric assessment, baPWV assessment and biochemical assessment were performed in 2906 T2D patients. CVAI was calculated from the combination of triglycerides, age, high-density lipoprotein cholesterol, waist circumference, body mass index. Multivariate regression analysis and generalized additive model were used to analyze the association between bapwv and CVAI. Subgroup analysis and interaction analysis were used to analyze the influencing factors.

Results

After adjustment for covariates, baPWV tended to increase in the quartiles of CVAI. In males, As CVAI increases by a unit, baPWV was increased by 0.28 cm/s (95% CI: -0.05, 0.61 P=0.0934). In females, As CVAI increases by a unit, baPWV was increased by 1.60 cm/s (95% CI: 1.07, 2.14). A non-linear connection in males and a linear connection in females between the CVAI and baPWV was revealed. In males, we found that CVAI interacted with baPWV in different duration of diabetes (P interaction = 0.0052), alcohol consumption status (P interaction = 0.0375). In females, CVAI interacted with baPWV in glycated hemoglobin (P interaction = 0.0003), systolic blood pressure (P interaction = 0.0001), diastolic blood pressure (P interaction<0.0001), duration of diabetes (P interaction = 0.0014), the use or non-use of glucose-lowering drugs (P interaction = 0.0006), the use or non-use antihypertensive drugs (P interaction = 0.0004), females' menopausal status (P interaction = 0.0012).

Conclusion

The relationship between CVAI and baPWV in T2D patients is positively non-linear in males and linear in females. In all subjects, this relationship was influenced by diabetes duration. In males, drinking status affected this relationship, and in females, It is influenced by blood pressure, glycemic control, menopausal status, and the use of glucose-lowering and hypotensive drug, highlighting the complex interplay between visceral fat and arterial stiffness in the T2D population.

Sex-specific responses in glucose-insulin homeostasis and lipoprotein-lipid components after high-dose supplementation with marine n-3 PUFAs in abdominal obesity: a randomized double-blind crossover study

Background

Clinical studies on effects of marine-derived omega-3 (n-3) polyunsaturated fatty acids (PUFAs), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and the plant-derived omega-6 (n-6) PUFA linoleic acid (LA) on lipoprotein-lipid components and glucose-insulin homeostasis have shown conflicting results, which may partly be explained by differential responses in females and males. However, we have lacked data on sexual dimorphism in the response of cardiometabolic risk markers following increased consumption of n-3 or n-6 PUFAs.

Objective

To explore sex-specific responses after n-3 (EPA + DHA) or n-6 (LA) PUFA supplementation on circulating lipoprotein subfractions, standard lipids, apolipoproteins, fatty acids in red blood cell membranes, and markers of glycemic control/insulin sensitivity among people with abdominal obesity.

Methods

This was a randomized double-blind crossover study with two 7-week intervention periods separated by a 9-week washout phase. Females (n = 16) were supplemented with 3 g/d of EPA + DHA (fish oil) or 15 g/d of LA (safflower oil), while males (n = 23) received a dose of 4 g/d of EPA + DHA or 20 g/d of LA. In fasting blood samples, we measured lipoprotein particle subclasses, standard lipids, apolipoproteins, fatty acid profiles, and markers of glycemic control/insulin sensitivity.

Results

The between-sex difference in relative change scores was significant after n-3 for total high-density lipoproteins (females/males: -11%*/-3.3%, p = 0.036; *: significant within-sex change), high-density lipoprotein particle size (+2.1%*/-0.1%, p = 0.045), and arachidonic acid (-8.3%*/-12%*, p = 0.012), and after n-6 for total (+37%*/+2.1%, p = 0.041) and small very-low-density lipoproteins (+97%*/+14%, p = 0.021), and lipoprotein (a) (-16%*/+0.1%, p = 0.028). Circulating markers of glucose-insulin homeostasis differed significantly after n-3 for glucose (females/males: -2.1%/+3.9%*, p = 0.029), insulin (-31%*/+16%, p < 0.001), insulin C-peptide (-12%*/+13%*, p = 0.001), homeostasis model assessment of insulin resistance index 2 (-12%*/+14%*, p = 0.001) and insulin sensitivity index 2 (+14%*/-12%*, p = 0.001), and quantitative insulin sensitivity check index (+4.9%*/-3.4%*, p < 0.001).

Conclusion

We found sex-specific responses after high-dose n-3 (but not n-6) supplementation in circulating markers of glycemic control/insulin sensitivity, which improved in females but worsened in males. This may partly be related to the sex differences we observed in several components of the lipoprotein-lipid profile following the n-3 intervention.

Clinical trial registration

https://clinicaltrials.gov/, identifier [NCT02647333].

Effect of Gender to Fat Deposition in Yaks Based on Transcriptomic and Metabolomics Analysis

Fat deposition in yaks plays an important part in survival, multiplication, and meat quality. In this work, the characteristic of fat deposition in male yaks (MYs) and female yaks (FYs) and the regulations of gender to yak fat deposition were explored by mRNA-Seq and non-targeted metabolomics analyses. FYs possessed a higher body fat rate (BFR) of visceral fat, fat content in longissimus dorsi (LD) and liver, and subcutaneous fat thickness (p < 0.05). The fat and cholesterol synthesis in liver and the fat transport in FY blood increased. The fat metabolism in yaks is the combined effect of carbohydrate, fatty acid, and amino acid metabolism by tricarboxylic acid (TCA) cycle, and an increase of triglyceride (TG) synthesis was accompanied by an increase of steroid synthesis. The high levels of myo-inositol and cortisol (COR) (p < 0.01) activated the calcium signaling in FY subcutaneous fat, followed by the increase of adipocyte secretion, and resulted in more leptin (LEP) secretion (p < 0.01). Then peroxisome proliferator-activated receptor (PPAR) signaling was activated by the focal adhesions and ECM-receptor interaction. Finally, the TG and steroid synthesis increased by the expression regulation of ME1, SCD, ELOVL6, DGAT2, DBI, LPL, CPT1, PLIN1, LIPA, DHCR24, and SQLE gene. The above genes can be considered as the candidate genes for yak with higher fat amount in molecular breeding in the future. This study can provide a theoretical basis for improving the meat quality and breeding of yaks.

Obesity-Related Changes in High-Density Lipoprotein Metabolism and Function

In obese individuals, atherogenic dyslipidemia is a very common and important factor in the increased risk of cardiovascular disease. Adiposity-associated dyslipidemia is characterized by low high-density lipoprotein cholesterol (HDL-C) levels and an increase in triglyceride-rich lipoproteins. Several factors and mechanisms are involved in lowering HDL-C levels in the obese state and HDL quantity and quality is closely related to adiponectin levels and the bioactive lipid sphingosine-1-phosphate. Recent studies have shown that obesity profoundly alters HDL metabolism, resulting in altered HDL subclass distribution, composition, and function. Importantly, weight loss through gastric bypass surgery and Mediterranean diet, especially when enriched with virgin olive oil, is associated with increased HDL-C levels and significantly improved metrics of HDL function. A thorough understanding of the underlying mechanisms is crucial for a better understanding of the impact of obesity on lipoprotein metabolism and for the development of appropriate therapeutic approaches. The objective of this review article was to summarize the newly identified changes in the metabolism, composition, and function of HDL in obesity and to discuss possible pathophysiological consequences.

Lipid Complications after Hematopoietic Stem Cell Transplantation (HSCT) in Pediatric Patients

HSCT (hematopoietic stem cell transplantation) is a widely applied method of treatment of pediatric patients with leukemia and other bone marrow-associated disorders. Metabolic disturbances can appear as procedure side effects. This study aimed to report incidence of lipid and thyroid disorders and time of their onset in pediatric patients after HSCT. There were 198 pediatric patients (123 males) aged 0.5–20 years who were subjected to HSCT. Patients were mostly diagnosed with Acute Leukemia (n = 190). The analysis of lipids, thyroid hormones, and thyroid antibodies levels comprised one month before the HSCT to last follow up visit between 2016 and 2019 (median 3.8 ± 1.8 years after HSCT). In males, the triglycerides levels increased over two times in the course of HSCT in both patients with initially low and elevated HDL (high-density lipoprotein) levels. Most of the lipid disorders occurred in six months after HSCT. Patients treated with L-thyroxine exhibited decreased LDL (low-density lipoprotein) levels. HDL remained at a lower level in males. Thyroid hormone abnormalities were evenly distributed in time until 4 years after HSCT. Patients require long term follow up including lipid metabolism and thyroid function analysis. HSCT survivors demand introduction of polyunsaturated fatty acids into the diet to reduce risk of developing the lipid complications.

The cross-sectional study of hepatic lipase SNPs and plasma lipid levels

By the combination of meta-analysis, the data of the 1,000 Genomes Project Phase 3, and the promoter sequence of hepatic lipase (LIPC), we performed the cross-sectional study to explore the associations of four variants (rs1077835; rs1077834; rs1800588 [C-514T], and rs2070895 [G-250A]) in LIPC promoter with plasma lipid levels. Our results indicate that the first and the next three of the four SNPs are, respectively, reported to be associated with the decreased and increased HDL-c level. Meta-analysis of 87 studies with 101,988 participants indicates that HDL-c level in rs1800588 (C-514T) (pooled mean difference = 0.03, 95%CI (0.03, 0.04), p < .001) and rs2070895 (G-250A) (pooled mean difference = 0.07, 95%CI (0.05, 0.09), p < .001) is higher in allele T or A carriers. Similarly, LDL-c, TC, TG, and BMI levels are generally increased in T or A alleles carriers. We failed to conduct the meta-analysis of rs1077835 and rs1077834 due to the limited previous reports. Data from the 1,000 Genomes indicate that the allele frequencies of the four SNPs in total or subpopulations are almost equal to each other. The paired value r 2 and D' of the four SNPs are larger than 0.8, which indicate the linkage disequilibrium of the four variants. The analysis of LIPC promoter indicate that C-514T and G-250A are, respectively, located in transcriptional factor binding sites of USF1and Pbx1b, which may partly explain the effect of the two SNPs on the decreased LIPC activity in the alleles carriers and the corresponding increased plasma lipids hydrolyzed by LIPC. These results may help us to better understand the different effects of the four SNPs on the plasma lipid levels among subpopulations and offer clues for future clinical treatment of dyslipidemia-related diseases.

Species differences in lipoprotein lipase and hepatic lipase activities: comparative studies of animal models of lifestyle-related diseases

Lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) have an important role in lifestyle-related diseases. To evaluate species differences, we compared LPL and HTGL activities in different animal models of lifestyle-related diseases using the same assay kit. Normal animals (JW rabbits, ICR mice, and SD rats), a hypercholesterolemic animal model (WHHLMI rabbits), and obese animal models (KK-A^y mice and Zucker fatty rats) fed standard chow were used in this study. Plasma was prepared before and after an intravenous injection of heparin sodium under fasting and feeding. LPL and HTGL activities were measured with the LPL/HTGL activity assay kit (Immuno-Biological Laboratories) using an auto-analyzer. Only in mice, high HTGL activity was observed in pre-heparin plasma. In normal animals, LPL and HTGL activities were high in ICR mice and SD rats but low in JW rabbits. Compared to normal animals, LPL activity was high in Zucker fatty rats and WHHLMI rabbits at both fasting and feeding, while LPL activity after feeding was low in KK-A^y mice. HTGL activity was higher in fasted and fed WHHLMI rabbits and fasted Zucker fatty rats, but was lower in fed KK-A^y mice. Gender difference was observed in HTGL activity in SD rats and LPL activity in WHHLMI rabbits but not in ICR mice. In conclusion, this simple assay method was effective for measuring LPL and HTGL activities of experimental animals, and the activities are highly regulated depending on animal species, animal models, feeding/fasting conditions and genders.

Subcutaneous Adipocyte Lipolysis Contributes to Circulating Lipid Levels

Supplemental Digital Content is available in the text.

Objective—

Fatty acids released via fat cell lipolysis can affect circulating lipid levels. However, the contribution of different lipolysis measures in adipose tissue is unknown and was presently examined in isolated subcutaneous adipocytes.

Approach and Results—

One thousand and sixty-six men and women were examined for lipolysis regulation in subcutaneous abdominal fat cells. Results were compared with fasting plasma levels of total cholesterol, high-density lipoprotein (HDL) cholesterol (HDL-C) and triglycerides. Spontaneous (basal) lipolysis and the effects of the major hormones stimulating (catecholamines and natriuretic peptides) and inhibiting lipolysis (insulin) were examined. Several statistically significant (P<0.0001) correlations between the different lipolysis parameters and plasma lipids were observed. However, physiologically relevant correlations (adjusted r²≥0.05) were only evident between basal or insulin-inhibited lipolysis and plasma triglycerides or HDL-C. Together, these lipolysis measures explained 14% of the variation in triglycerides or HDL-C, respectively. In comparison, a combination of established factors associated with variations in plasma lipids, that is, age; body mass index; waist circumference; waist-to-hip ratio; sex; nicotine use; fat cell volume; and pharmacotherapy against diabetes mellitus; hypertension; or hyperlipidemia explained 17% and 28%, respectively, of the variations in plasma triglycerides and HDL-C.

Conclusions—

Subcutaneous fat cell lipolysis is an important independent contributor to interindividual variations in plasma lipids. High spontaneous lipolysis activity and resistance to the antilipolytic effect of insulin associate with elevated triglyceride and low HDL-C concentrations. Thus, although several other factors also play a role, subcutaneous adipose tissue may have a causal influence on dyslipidemia.

Insulin Clearance Is Associated with Hepatic Lipase Activity and Lipid and Adiposity Traits in Mexican Americans

Reduction in insulin clearance plays an important role in the compensatory response to insulin resistance. Given the importance of this trait to the pathogenesis of diabetes, a deeper understanding of its regulation is warranted. Our goal was to identify metabolic and cardiovascular traits that are independently associated with metabolic clearance rate of insulin (MCRI). We conducted a cross-sectional analysis of metabolic and cardiovascular traits in 765 participants from the Mexican-American Coronary Artery Disease (MACAD) project who had undergone blood sampling, oral glucose tolerance test, euglycemic-hyperinsulinemic clamp, dual-energy X-ray absorptiometry, and carotid ultrasound. We assessed correlations of MCRI with traits from seven domains, including anthropometry, biomarkers, cardiovascular, glucose homeostasis, lipase activity, lipid profile, and liver function tests. We found inverse independent correlations between MCRI and hepatic lipase (P = 0.0004), insulin secretion (P = 0.0002), alanine aminotransferase (P = 0.0045), total fat mass (P = 0.014), and diabetes (P = 0.03). MCRI and apolipoprotein A-I exhibited a positive independent correlation (P = 0.035). These results generate a hypothesis that lipid and adiposity associated traits related to liver function may play a role in insulin clearance.

Gender specific effect of LIPC C-514T polymorphism on obesity and relationship with plasma lipid levels in Chinese children

Hepatic lipase (LIPC) is a key rate-limiting enzyme in lipoprotein catabolism pathways involved in the development of obesity. The C-514T polymorphism in the promoter region is associated with decreased LIPC activity. We performed a case-controlled study (850 obese children and 2119 controls) and evaluated the association between LIPC C-514T polymorphism, obesity and plasma lipid profile in Chinese children and adolescents. Additionally, we conducted a meta-analysis of all results from published studies as well as our own data. A significant association between the polymorphism and obesity is observed in boys (P = 0.042), but not in girls. And we observed a significant relationship of the polymorphism with total cholesterol (TC) and high density lipoprotein cholesterol (HDL-C) independent of obesity in boys. The T allele carriers have higher levels of low density lipoprotein cholesterol (LDL-C) in obese boys, and triglyceride (TG), TC and LDL-C in non-obese girls (all P < 0.05). In the meta-analysis, under dominant model the T allele increased body mass index (BMI) level in boys, while it decreased BMI in girls, and increased the levels of TC both in the overall and subgroups, TG and HDL-C in the overall and boys, and LDL-C in the overall (all P < 0.05). Our results suggest that the T allele might carry an increased risk of obesity in Chinese boys. The meta-analysis suggests that T allele acts as a risk allele for higher BMI levels in male childhood, while it is a protective allele in female childhood. And the polymorphism is associated with the levels of plasma lipids, which may be modulated by obesity and gender.

In vivo structure-function studies of human hepatic lipase: the catalytic function rescues the lean phenotype of HL-deficient (hl-/-) mice

The lean body weight phenotype of hepatic lipase (HL)-deficient mice (hl(-/-)) suggests that HL is required for normal weight gain, but the underlying mechanisms are unknown. HL plays a unique role in lipoprotein metabolism performing bridging as well as catalytic functions, either of which could participate in energy homeostasis. To determine if both the catalytic and bridging functions or the catalytic function alone are required for the effect of HL on body weight, we studied (hl(-/-)) mice that transgenically express physiologic levels of human (h)HL (with catalytic and bridging functions) or a catalytically-inactive (ci)HL variant (with bridging function only) in which the catalytic Serine 145 was mutated to Alanine. As expected, HL activity in postheparin plasma was restored to physiologic levels only in hHL-transgenic mice (hl(-/-)hHL). During high-fat diet feeding, hHL-transgenic mice exhibited increased body weight gain and body adiposity relative to hl(-/-)ciHL mice. A similar, albeit less robust effect was observed in female hHL-transgenic relative to hl(-/-)ciHL mice. To delineate the basis for this effect, we determined cumulative food intake and measured energy expenditure using calorimetry. Interestingly, in both genders, food intake was 5-10% higher in hl(-/-)hHL mice relative to hl(-/-)ciHL controls. Similarly, energy expenditure was ~10% lower in HL-transgenic mice after adjusting for differences in total body weight. Our results demonstrate that (1) the catalytic function of HL is required to rescue the lean body weight phenotype of hl(-/-) mice; (2) this effect involves complementary changes in both sides of the energy balance equation; and (3) the bridging function alone is insufficient to rescue the lean phenotype of hl(-/-)ciHL mice.

Obesity and its metabolic complications: the role of adipokines and the relationship between obesity, inflammation, insulin resistance, dyslipidemia and nonalcoholic fatty liver disease

Accumulating evidence indicates that obesity is closely associated with an increased risk of metabolic diseases such as insulin resistance, type 2 diabetes, dyslipidemia and nonalcoholic fatty liver disease. Obesity results from an imbalance between food intake and energy expenditure, which leads to an excessive accumulation of adipose tissue. Adipose tissue is now recognized not only as a main site of storage of excess energy derived from food intake but also as an endocrine organ. The expansion of adipose tissue produces a number of bioactive substances, known as adipocytokines or adipokines, which trigger chronic low-grade inflammation and interact with a range of processes in many different organs. Although the precise mechanisms are still unclear, dysregulated production or secretion of these adipokines caused by excess adipose tissue and adipose tissue dysfunction can contribute to the development of obesity-related metabolic diseases. In this review, we focus on the role of several adipokines associated with obesity and the potential impact on obesity-related metabolic diseases. Multiple lines evidence provides valuable insights into the roles of adipokines in the development of obesity and its metabolic complications. Further research is still required to fully understand the mechanisms underlying the metabolic actions of a few newly identified adipokines.

Chromosome imbalance as a driver of sex disparity in disease

It has long been recognized that men and women exhibit different risks for diverse disorders ranging from metabolic to autoimmune diseases. However, the underlying causes of these disparities remain obscure. Analysis of patients with chromosomal abnormalities, including Turner syndrome (45X) and Klinefelter syndrome (47XXY), has highlighted the importance of X-linked gene dosage as a contributing factor for disease susceptibility. Escape from X-inactivation and X-linked imprinting can result in transcriptional differences between normal men and women as well as in patients with sex chromosome abnormalities. Animal models support a role for X-linked gene dosage in disease with O-linked N-acetylglucosamine transferase (OGT) emerging as a prime candidate for a pleiotropic effector. OGT encodes a highly regulated nutrient-sensing epigenetic modifier with established links to immunity, metabolism and development.

Role of SN1 lipases on plasma lipids in metabolic syndrome and obesity

OBJECTIVE

To assess the phospholipase activity of endothelial (EL) and hepatic lipase (HL) in postheparin plasma of subjects with metabolic syndrome (MS)/obesity and their relationship with atherogenic and antiatherogenic lipoproteins. Additionally, to evaluate lipoprotein lipase (LPL) and HL activity as triglyceride (TG)-hydrolyses to complete the analyses of SN1 lipolytic enzymes in the same patient.

APPROACH AND RESULTS

Plasma EL, HL, and LPL activities were evaluated in 59 patients with MS and 36 controls. A trend toward higher EL activity was observed in MS. EL activity was increased in obese compared with normal weight group (P=0.009) and was negatively associated with high-density lipoprotein-cholesterol (P=0.014 and P=0.005) and apolipoprotein A-I (P=0.045 and P=0.001) in control and MS group, respectively. HL activity, as TG-hydrolase, was increased in MS (P=0.025) as well as in obese group (P=0.017); directly correlated with low-density lipoprotein-cholesterol (P=0.005) and apolipoprotein B (P=0.003) and negatively with high-density lipoprotein-cholesterol (P=0.021) in control group. LPL was decreased in MS (P<0.001) as well as in overweight and obese compared with normal weight group (P=0.015 and P=0.004, respectively); inversely correlated %TG-very low-density lipoproteins (P=0.04) and TG/apolipoprotein B index (P=0.013) in control group. These associations were not found in MS.

CONCLUSIONS

We describe for the first time EL and HL activity as phospholipases in MS/obesity, being both responsible for high-density lipoprotein catabolism. Our results elucidate part of the remaining controversies about SN1 lipases activity in MS and different grades of obesity. The impact of insulin resistance on the activity of the 3 enzymes determines the lipoprotein alterations observed in these states.

Fat depots, free fatty acids, and dyslipidemia

Body fat deposition and excess free fatty acid (FFA) metabolism contribute to dyslipidemia and the adverse health consequences of obesity. Individuals with upper body obesity have impaired functioning of adipocytes, the primary fatty acid storage site. Excess visceral fat is strongly associated with impaired suppression of FFA release in response to insulin, as well as with hypertriglyceridemia and low concentrations of high density lipoprotein (HDL) cholesterol. High FFA concentrations can induce insulin resistance in muscle and liver. Furthermore, failure of hyperinsulinemia to normally suppress FFA is associated with impaired carbohydrate oxidation and muscle glucose storage, reduced hepatic insulin clearance and elevated triglycerides. Understanding the impact of body fat distribution on FFA metabolism and dyslipidemia is critical for determining the link between overweight and obesity and cardiovascular disease risk. In the current review, we will explore the relationship between adipose tissue, body fat depots, and FFA metabolism.

Cardiovascular risk factors in middle age obese Indians: a cross-sectional study on association of per cent body fat and intra-abdominal fat mass

OBJECTIVES

To determine the association of per cent total body fat (TBF), intra-abdominal fat (IAF) mass and subcutaneous abdominal fat with cardiovascular risk factors in middle age obese Indians.

DESIGN

Cross-sectional study.

SETTING

Hydrostatic Laboratory, Department of Sports Medicine and Physiotherapy, Guru Nanak Dev University, India.

PARTICIPANTS

51 subjects aged 30-55 years with a body mass index value 23 and above.

METHODOLOGY

In all the participants, TBF was estimated by underwater weighing machine and IAF and subcutaneous fat were measured by ultrasonography. Lipid profile was determined by a semiautomated analyser. Main outcome measures were: IAF, per cent body fat to TBF ratio, lipid profile and risk of developing cardiovascular diseases.

RESULTS

IAF was found to be significantly associated with lipid variables (95% CI, p<0.01) and risk of developing cardiovascular diseases (95% CI, p≤0.05) in both male and female subjects. TBF and subcutaneous fat thickness showed no significant results (95% CI, p>0.05) with either lipid variables or risk of developing cardiovascular diseases (tables 1 and 2). IAF mass showed significant association with age (95% CI, p<0.01) and significant negative association with physical activity (95% CI, p<0.05) in male subjects (tables 3 and 4).

CONCLUSION

An ultrasonic measurement of IAF is a better predictor of the risk of developing cardiovascular diseases in middle aged Indian population. In male subjects, physical activity of 5 or more days a week showed lesser amount of IAF as compared with those with physical activity <5 days a week.

Positive association of the hepatic lipase gene polymorphism c.514C > T with estrogen replacement therapy response

Background

Hepatic lipase (HL), an enzyme present in the hepatic sinusoids, is responsible for the lipolysis of lipoproteins. Human HL contains four polymorphic sites: G-250A, T-710C, A-763G, and C-514T single-nucleotide polymorphism (SNPs). The last polymorphism is the focus of the current study. The genotypes associated with the C-514T polymorphism are CC (normal homozygous - W), CT (heterozygous - H), and TT (minor-allele homozygous - M). HL activity is significantly impaired in individuals of the TT and CT genotypes. A total of 58 post-menopausal women were studied. The subjects were hysterectomized women receiving hormone replacement therapy consisting of 0.625 mg of conjugated equine estrogen once a day. The inclusion criteria were menopause of up to three years and normal blood tests, radiographs, cervical-vaginal cytology, and densitometry. DNA was extracted from the buccal and blood cells of all 58 patients using a commercially available kit (GFX^® - Amersham-Pharmacia, USA).

Results

Statistically significant reductions in triglycerides (t = 2.16; n = 58; p = 0.03) but not in total cholesterol (t = 0.14; n = 58; p = 0.89) were found after treatment. This group of good responders were carriers of the T allele; the CT and TT genotypes were present significantly more frequently than in the group of non-responders (p = 0.02 or p = 0.07, respectively). However, no significant difference in HDL-C (t = 0.94; n = 58; p = 0.35) or LDL-C (t = -0.83; n = 58; p = 0.41) was found in these patients.

Conclusions

The variation in lipid profile associated with the C-514T polymorphism is significant, and the T allele is associated with the best response to ERT.

New insights into the mechanism of low high-density lipoprotein cholesterol in obesity

Obesity, a significant risk factor for various chronic diseases, is universally related to dyslipidemia mainly represented by decreasing high-density lipoprotein cholesterol (HDL-C), which plays an indispensible role in development of cardiovascular disease (CVD). However, the mechanisms underlying obesity and low HDL-C have not been fully elucidated. Previous studies have focused on the alteration of HDL catabolism in circulation following elevated triglyceride (TG). But recent findings suggested that liver and fat tissue played pivotal role in obesity related low HDL-C. Some new molecular pathways like microRNA have also been proposed in the regulation of HDL metabolism in obesity. This article will review recent advances in understanding of the potential mechanism of low HDL-C in obesity.

The effect of hepatic lipase on coronary artery disease in humans is influenced by the underlying lipoprotein phenotype

Increased or decreased hepatic lipase (HL) activity has been associated with coronary artery disease (CAD). This is consistent with the findings that gene variants that influence HL activity were associated with increased CAD risk in some population studies but not in others. In this review, we will explain the conditions that influence the effects of HL on CAD. Increased HL is associated with smaller and denser LDL (sdLDL) and HDL (HDL(3)) particles, while decreased HL is associated with larger and more buoyant LDL and HDL particles. The effect of HL activity on CAD risk is dependent on the underlying lipoprotein phenotype or disorder. Central obesity with hypertriglyceridemia (HTG) is associated with high HL activity that leads to the formation of sdLDL that is pro-atherogenic. In the absence of HTG, where large buoyant cholesteryl ester-enriched LDL is prominent, elevation of HL does not raise the risk for CAD. In HTG patients, drug therapy that decreases HL activity selectively decreases sdLDL particles, an anti-atherogenic effect. Drug therapy that raises HDL(2) cholesterol has not decreased the risk for CAD. In trials where inhibition of cholesterol ester transfer protein (CETP) or HL occurs, the increase in HDL(2) most likely is due to inhibition of catabolism of HDL(2) and impairment of reverse cholesterol transport (RCT). In patients with isolated hypercholesterolemia, but with normal triglyceride levels and big-buoyant LDL particles, an increase in HL activity is beneficial; possibly because it increases RCT. Drugs that lower HL activity might decrease the risk for CAD only in hypertriglyceridemic patients with sdLDL by selectively clearing sdLDL particles from plasma, which would override the potentially pro-atherogenic effect on RCT. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).

A higher burden of small low-density lipoprotein particles is associated with profound changes in the free androgen index in male adolescents

From a young age, males are at higher cardiovascular risk than females. Dyslipidemia, including a higher burden related to small low-density lipoproteins (LDL), plays an important role in precipitating atherosclerosis in both males and females. We investigated sex differences in atherogenic lipoprotein burden and the independent predictors of LDL particle size in children and adolescents. We measured the concentrations of total testosterone, sex hormone-binding globulin, estradiol, total cholesterol, triglyceride, LDL cholesterol, HDL cholesterol, and LDL particle size in 135 children and adolescents (67 boys, 68 girls). The free androgen index was significantly and negatively correlated with LDL particle size (r = -0.273, P = 0.026) in boys, but estrogen and LDL particle size were not related. In a stepwise multiple regression analysis adjusted for body mass index, age, and homeostasis model assessment for insulin resistance, free androgen index was still an independent predictor of LDL particle size in boys (R(2) = 0.075, P = 0.026). The prominent decrease in LDL particle size along with increased testosterone concentrations in males might explain why they are more likely to display atherogenic dyslipidemia from adolescence.

LIPC variants in the promoter and intron 1 modify HDL-C levels in a sex-specific fashion

We previously reported linkage for plasma levels of high-density lipoprotein cholesterol (HDL-C) on 15q21 in Caucasian families from the National Heart, Lung, and Blood Institute Family Heart Study (NHLBI FHS). Hepatic lipase gene (LIPC), which has a major role in lipoprotein metabolism, resides within the linkage region and constitutes an obvious candidate gene. While hepatic lipase is a known player in HDL metabolism, the relationship between common LIPC variants and HDL-C levels remains unclear. In the current study, we employed population-based and family-based tests of association with both quantitative HDL-C levels and a dichotomous dyslipidemia trait (affected men: HDL<40 mg/dL and women: HDL<50 mg/dL, denoted as low HDL). We genotyped 19 tag-SNPs spanning 139.9 kb around the LIPC in the 591 families (2238 subjects). Strong association in a proxy-promoter 5' SNP (rs261342) and HDL-C levels was detected in women, but not in men. The less common allele was associated with an increase of approximately 14% in HDL-C levels, and a decrease of approximately 30% in risk of low HDL. In addition, strong association in women of an intron 1 SNP (rs12593008) and low HDL and moderate association in men (rs8028759) with both HDL-C levels and low HDL phenotype were found and may represent either functional single nucleotide polymorphisms (SNPs), or more likely, SNPs in linkage disequilibrium with functional variants. Because of the association of lipid abnormalities with diabetes, and other lifestyle parameters, we also performed association analyses using different covariate adjustments as well as strategically selected sub-samples. The sex-specific association of rs261342, rs12593008 or rs8028759 remained substantially the same through these analyses. Finally, we found that a common haplotype was overtransmitted to offspring with low HDL-C. The sex-specific associations found in our study could be due to the interactions with the endogenous hormonal environment, lifestyle and/or genetic factors, although the underlying physiologic mechanisms are not understood.

Activation of hepatic lipase expression by oleic acid: possible involvement of USF1

Polyunsaturated fatty acids affect gene expression mainly through peroxisome proliferator-activated receptors (PPARs) and sterol regulatory element binding proteins (SREBPs), but how monounsaturated fatty acids affect gene expression is poorly understood. In HepG2 cells, oleate supplementation has been shown to increase secretion of hepatic lipase (HL). We hypothesized that oleate affects HL gene expression at the transcriptional level. To test this, we studied the effect of oleate on HL promoter activity using HepG2 cells and the proximal HL promoter region (700 bp). Oleate increased HL expression and promoter activity 1.3-2.1 fold and reduced SREBP activity by 50%. Downregulation of SREBP activity by incubation with cholesterol+25-hydroxycholesterol had no effect on HL promoter activity. Overexpression of SREBP2, but not SREBP1, reduced HL promoter activity, which was effected mainly through the USF1 binding site at -307/-312. Oleate increased the nuclear abundance of USF1 protein 2.7 ± 0.6 fold, while USF1 levels were reduced by SREBP2 overexpression. We conclude that oleate increases HL gene expression via USF1. USF1 may be an additional fatty acid sensor in liver cells.

Effect of obesity on the plasma lipoprotein subclass profile in normoglycemic and normolipidemic men and women

OBJECTIVE

To determine the effect of obesity without the confounding effect of metabolic complications on the lipoprotein subclass profile in men and women.

DESIGN

Cross-sectional study.

SUBJECTS

A total of 40 lean (body mass index (BMI): 18.5-25 kg/m(2)) and 40 obese (BMI: 30-45 kg/m(2)) subjects, with blood pressure <140/90 mm Hg, fasting plasma glucose concentration <100 mg per 100 ml and total triglyceride concentration <150 mg per 100 ml; all obese subjects had normal oral glucose tolerance.

MEASUREMENTS

Fasting concentrations of very low-, intermediate-, low- and high-density lipoproteins (VLDL, IDL, LDL, and HDL, respectively) and average VLDL, LDL and HDL particle sizes were evaluated by using proton nuclear magnetic resonance spectroscopy.

RESULTS

Obese compared with lean individuals of both sexes had increased plasma concentrations of VLDL (by approximately 50%), IDL (by approximately 100%), LDL (by approximately 50%), and to some extent HDL (by approximately 10%) particles (P<0.05). The contribution of large VLDL to total VLDL concentration, small LDL to total LDL concentration, and small HDL to total HDL concentration was greater in obese than lean subjects (P<0.05), resulting in larger average VLDL size but smaller average LDL and HDL sizes (P<0.05). Women, compared with men, had reduced concentrations of total VLDL particles (by approximately 10%) due to lower concentrations of large and medium VLDL and a shift toward large at the expense of small HDL particles (P<0.05), with no difference in total HDL particle concentration. IDL and total LDL concentrations and LDL subclass distribution were not different between men and women.

CONCLUSION

Obesity is associated with pro-atherogenic alterations in the lipoprotein subclass profile, which may increase cardiovascular disease risk even in the absence of classical metabolic risk factors. On the other hand, the female cardiovascular disease risk advantage is probably largely related to differences in traditional lipid risk factors (plasma triglyceride and HDL-cholesterol concentrations) because sex differences in the plasma lipoprotein subclass profile are minimal.

Endothelial lipase concentrations are increased in metabolic syndrome and associated with coronary atherosclerosis

BACKGROUND

Endothelial lipase (EL), a new member of the lipase family, has been shown to modulate high-density lipoprotein (HDL-C) metabolism and atherosclerosis in mouse models. We hypothesized that EL concentrations would be associated with decreased HDL-C and increased atherosclerosis in humans.

METHODS AND FINDINGS

Healthy individuals with a family history of premature coronary heart disease (n = 858) were recruited as part of the Study of the Inherited Risk of Atherosclerosis. Blood was drawn in the fasting state before and, in a subgroup (n = 510), after administration of a single dose of intravenous heparin. Plasma lipids were measured enzymatically, lipoprotein subclasses were assessed by nuclear magnetic resonance, and coronary artery calcification (CAC) was quantified by electron beam computed tomography. Plasma EL mass was measured using a newly developed enzyme-linked immunosorbent assay. Median EL mass in pre-heparin plasma was 442 (interquartile range = 324-617) ng/ml. Median post-heparin mass was approximately 3-fold higher, 1,313 (888-1,927) ng/ml. The correlation between pre-heparin EL mass and post-heparin EL mass was 0.46 (p < 0.001). EL mass concentrations in both pre- and post-heparin plasma significantly correlated with all NCEP ATPIII-defined metabolic syndrome factors: waist circumference (r = 0.28 and 0.22, respectively, p < 0.001 for each), blood pressure (r = 0.18 and 0.24, p < 0.001 for each), triglycerides (r = 0.22, p < 0.001; and 0.13, p = 0.004), HDL cholesterol (r = -0.11, p = 0.002; and -0.18, p < 0.001), and fasting glucose (r = 0.11 and 0.16, p = 0.001 for both). EL mass in both routine (odds ratio [OR] = 1.67, p = 0.01) and post-heparin (OR = 2.42, p = 0.003) plasma was associated with CAC as determined by ordinal regression after adjustment for age, gender, waist circumference, vasoactive medications, hormone replacement therapy (women), and established cardiovascular risk factors.

CONCLUSIONS

We report, to our knowledge for the first time, that human plasma EL concentrations, in both post-heparin and routine pre-heparin plasma, are significantly associated with metabolic syndrome features and with subclinical atherosclerosis. EL may be a pro-atherogenic factor in humans, especially in overweight individuals and those with metabolic syndrome.

Hepatic lipase: friend or foe and under what circumstances?

Hepatic lipase (HL) plays a role in the metabolism of chylomicron and very low-density lipoprotein remnants, low-density lipoproteins (LDL), and high-density lipoproteins (HDL), which are all implicated in atherosclerosis. Considering the effects of HL on these lipoproteins, it appears that HL has pro- as well as antiatherogenic potential. In line with clinical observations, most effects of HL on lipoprotein metabolism during hypertriglyceridemia may be interpreted as promoting atherosclerosis (formation of small, dense LDL, lowering of HDL levels), whereas most effects during hypercholesterolemia seem to be potentially antiatherogenic (stimulation of reverse cholesterol transport, clearing of intermediate-density lipoprotein). The potential modulation of pro- or antiatherogenics effect of HL by other factors, such as LDL receptor, cholesterol ester transfer protein, lipoprotein lipase, and ATP-binding cassette A-1 activity, is discussed.