Regulation of Plasma fatty acid metabolism

Lipoprotein Ratios: Correlation With Glycated Hemoglobin (HbA1c) Among Thyroid Disorders' Patients

INTRODUCTION

Thyroid disorders and diabetes mellitus are prevalent conditions in the modern era. Moreover, glycated hemoglobin (HbA1c) is the established (prognostic as well as diagnostic) marker for long-term glycemic control, whereas the lipid profile is the marker for cardiovascular risks. The association of hypothyroidism with dyslipidemia is also a well-established fact. The current study explores a correlation between thyroid profile, glycemic status, and various lipoprotein indices.

OBJECTIVE

To look for an association between thyroid profile, glycemic status, and various lipoprotein indices.

METHODOLOGY

The cross-sectional study conducted at AIIMS Gorakhpur included a total of 108 subjects, with 37 normal subjects (Group I) and 71 patients) with T2DM (Type-2 diabetes mellitus) (Group II). Baseline characteristics of the two groups were compared for age, sex, presence of hypertension, fasting blood glucose, and body mass index (BMI). Blood samples were collected from the patients. The sera were analyzed for HbA1c and lipid profile, which included total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C). Serum samples were also used to estimate the thyroid stimulating hormone (TSH) and triiodothyronine (fT3). The association between thyroid profile, glycemic status, and various lipoprotein indices was calculated.

STATISTICAL ANALYSIS

 Kolmogorov-Smirnov test for normality of the data. Spearmann correlation was used for nonparametric data.

RESULTS

There were significantly higher levels of total cholesterol, triglycerides, and LDL-C levels in T2DM subjects than in non-diabetic subjects. There was also a significant positive correlation observed between TSH and TC among the normal control group (ρ =0.348, P=0.04). Similarly, significant positive correlations were found for TG (ρ =0.354, P=0.04) and LDL-C (ρ =0.431, P=0.03) among non-diabetic subjects. Among patients with T2DM, TSH was significantly correlated positively with TG (ρ =0.530, P=0.006) and LDL-C (ρ =0.443, P=0.03). Similarly, in the same group, among lipid ratios, TG/HDL-C (ρ =0.311, P=0.04) and LDL-C/HDL-C (ρ =0.227, P=0.05) were significantly correlated to TSH. Furthermore, there were significant positive correlations between TSH and HbA1c (ρ =0.301, P=0.04). fT3 was found to have a strong negative correlation with HbA1c among patients with T2DM (ρ =-0.454, P=0.02).

CONCLUSION

Thyroid disorders exert significant effects on glycemic control and lipid metabolism, which may impact HbA1c levels and lipid profile parameters.

Cardiometabolic Risk Factors Associated With Type 2 Diabetes Mellitus: A Mechanistic Insight

A complex metabolic condition referred to as Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance (IR) and decreased insulin production. Obesity, dyslipidemia, hypertension, and chronic inflammation are just a few of the cardiometabolic illnesses that people with T2DM are more likely to acquire and results in cardiovascular issues. It is essential to comprehend the mechanistic insights into these risk variables in order to prevent and manage cardiovascular problems in T2DM effectively. Impaired glycemic control leads to upregulation of De novo lipogenesis (DNL), promote hepatic triglyceride (TG) synthesis, worsening dyslipidemia that is accompanied by low levels of high density lipoprotein cholesterol (HDL-C) and high amounts of small, dense low-density lipoprotein cholesterol (LDL-C) further developing atherosclerosis. By causing endothelial dysfunction, oxidative stress, and chronic inflammation, chronic hyperglycemia worsens already existing cardiometabolic risk factors. Vasoconstriction, inflammation, and platelet aggregation are caused by endothelial dysfunction, which is characterized by decreased nitric oxide production, increased release of vasoconstrictors, proinflammatory cytokines, and adhesion molecules. The loop of IR and endothelial dysfunction is sustained by chronic inflammation fueled by inflammatory mediators produced in adipose tissue. Infiltrating inflammatory cells exacerbate inflammation and the development of plaque in the artery wall. In addition, the combination of chronic inflammation, dyslipidemia, and IR contributes to the emergence of hypertension, a prevalent comorbidity in T2DM. The ability to target therapies and management techniques is made possible by improvements in our knowledge of these mechanistic insights. Aim of present review is to enhance our current understanding of the mechanistic insights into the cardiometabolic risk factors related to T2DM provides important details into the interaction of pathophysiological processes resulting in cardiovascular problems. Understanding these pathways will enable us to create efficient plans for the prevention, detection, and treatment of cardiovascular problems in T2DM patients, ultimately leading to better overall health outcomes.

Apolipoprotein A-IV-Deficient Mice in 129/SvJ Background Are Susceptible to Obesity and Glucose Intolerance

Apolipoprotein A-IV (apoA-IV), synthesized by enterocytes, is potentially involved in regulating lipid absorption and metabolism, food intake, and glucose metabolism. In this study, we backcrossed apoA-IV knockout (apoA-IV-/-) mice onto the 129/SvJ background for eight generations. Compared to the wild-type (WT) mice, the 129/SvJ apoA-IV-/- mice gained more weight and exhibited delayed glucose clearance even on the chow diet. During a 16-week high-fat diet (20% by weight of fat) study, apoA-IV-/- mice were more obese than the WT mice, which was associated with their increased food intake as well as reduced energy expenditure and physical activity. In addition, apoA-IV-/- mice developed significant insulin resistance (indicated by HOMA-IR) with severe glucose intolerance even though their insulin levels were drastically higher than the WT mice. In conclusion, we have established a model of apoA-IV-/- mice onto the 129/SvJ background. Unlike in the C57BL/6J strain, apoA-IV-/- 129/SvJ mice become significantly more obese and insulin-resistant than WT mice. Our current investigations of apoA-IV in the 129/SvJ strain and our previous studies in the C57BL/6J strain underline the impact of genetic background on apoA-IV metabolic effects.

Mulberry (Morus alba L.) ethanol extract attenuates lipid metabolic disturbance and adipokine imbalance in high-fat fed rats

BACKGROUND/OBJECTIVES

An imbalanced adipokine profile in obesity increases the susceptibility to obesity-related cardiometabolic alterations, including type 2 diabetes, hypertension, dyslipidemia, and non-alcoholic fatty liver disease. The mulberry plant has been reported to have health benefits, such as hypolipidemic and hepatoprotective effects. This study examined the effects of a mulberry (Morus alba L.) fruit ethanol extract (MBEE) on dyslipidemia, liver steatosis, and adipokine imbalance in response to a high-fat diet.

MATERIALS/METHODS

Male Sprague-Dawley rats were assigned to one of 4 groups containing 6 rats each and fed either a control diet (CON), a high-fat diet (HFD), or a high-fat diet with MBEE of 150 mg/kg/day (LMB) or 300 mg/kg/day (HMB). The triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activities were measured spectrophotometrically. The leptin, adiponectin, and plasminogen activator inhibitor-1 (PAI-1) levels were determined by an enzyme-linked immunosorbent assay.

RESULTS

The plasma TG levels were similar in the 4 groups. Plasma cholesterol and low-density lipoprotein cholesterol (LDL-C) levels and TC/HDL-C ratio increased in the HFD group compared with the CON group, whereas those values decreased in the LMB group (P < 0.05), indicating that MBEE had a plasma lipid-lowering effect. HDL-C decreased in the HFD group, but MBEE did not affect the HDL-C level. The HFD rats significantly increased hepatic TG and cholesterol levels and plasma ALT and AST activities compared to the CON group. The hepatic TG level and ALT and AST activities were reduced markedly by the MBEE treatment. The HFD group showed a higher PAI-1 level, whereas MBEE treatment, especially in the HMB group, significantly reduced leptin level, and leptin/adiponectin and PAI-1/adiponectin ratios. These findings suggest that MBEE altered the imbalance between the pro- and anti-inflammatory adipokines to a more anti-inflammatory state.

CONCLUSIONS

MBEE could protect against abnormal lipid metabolism and hepatic steatosis induced by a high-fat diet, lowering plasma cholesterol, LDL-C and TC/HDL-C, and hepatic TG. These findings are associated with the regulating effect of MBEE on the leptin/adiponectin and PAI-1/adiponectin ratios.

Gemfibrozil improves lipid metabolism in Nile tilapia Oreochromis niloticus fed a high-carbohydrate diet through peroxisome proliferator activated receptor-α activation

High carbohydrate diet (HCD) can induce lipid metabolism disorder, characterized by excessive lipid in farmed fish. Peroxisome proliferator activated receptor-α (PPARα) plays an important role in lipid homeostasis. In this study, we hypothesize that PPARα can improve lipid metabolism in fish fed HCD. Fish (3.03 ± 0.11 g) were fed with three diets: control (30% carbohydrate), HCD (45% carbohydrate) and HCG (HCD supplemented with 200 mg/kg gemfibrozil, an agonist of PPARα) for eight weeks. The fish fed HCG had higher growth rate and protein effiency than those fed the HCD diet, whereas the opposite trend was observed in feed conversion ratio, hepatosomatic index and mesenteric fat index. Additionally, fish fed HCG significantly decreased lipid accumulation in the whole body, liver and adipose tissues compared to those fed the HCD diet. Furthermore, fish in the HCG group significantly increased the mRNA and protein expression and protein dephosphorylation of PPARα. The HCG group also significantly increased the mRNA level of the downstream target genes of PPARα, whereas the opposite trend occured in the mRNA level of lipolysis-related genes compared to the HCD group. Besides, fish in the HCG group remarkably decreased the contents of alanine aminotransferase, aspartate aminotransferase and malondialdehyde, whereas the opposite occured in the activities of antioxidative enzymes and anti-inflammatory cytokine genes compared to the HCD group. This study indicates that gemfibrozil can improve lipid metabolism and maintain high antioxidant and anti-inflammatory capacity through activating PPARα in Nile tilapia fed a high carbohydrate diet.

Current Progress of Lipid Analysis in Metabolic Diseases by Mass Spectrometry Methods

BACKGROUND

Obesity, insulin resistance, diabetes, and metabolic syndrome are associated with lipid alterations, and they affect the risk of long-term cardiovascular disease. A reliable analytical instrument to detect changes in the composition or structures of lipids and the tools allowing to connect changes in a specific group of lipids with a specific disease and its progress, is constantly lacking. Lipidomics is a new field of medicine based on the research and identification of lipids and lipid metabolites present in human organism. The primary aim of lipidomics is to search for new biomarkers of different diseases, mainly civilization diseases.

OBJECTIVE

We aimed to review studies reporting the application of mass spectrometry for lipid analysis in metabolic diseases.

METHOD

Following an extensive search of peer-reviewed articles on the mass spectrometry analysis of lipids the literature has been discussed in this review article.

RESULTS

The lipid group contains around 1.7 million species; they are totally different, in terms of the length of aliphatic chain, amount of rings, additional functional groups. Some of them are so complex that their complex analyses are a challenge for analysts. Their qualitative and quantitative analysis of is based mainly on mass spectrometry.

CONCLUSION

Mass spectrometry techniques are excellent tools for lipid profiling in complex biological samples and the combination with multivariate statistical analysis enables the identification of potential diagnostic biomarkers.

Sex-specific relationship between visceral fat index and dyslipidemia in Chinese rural adults: The Henan Rural Cohort Study

The study aimed to explore the relationship between visceral fat index (VFI) and dyslipidemia and evaluate the efficiency of VFI as a marker for identifying dyslipidemia in Chinese rural adults. The cross-sectional study recruited 35,832 aged 18-79 years eligible participants from The Henan Rural Cohort Study. VFI was measured by bioelectrical impendence methods and classified into sex-specific quartiles. Fasting blood samples were collected. Logistic regression models with VFI as a categorical variable and restricted cubic spline regression models with VFI as a continuous variable were performed to obtain odds ratios (ORs) and 95% confidence intervals (CIs). Receiver-operating characteristic (ROC) curve was conducted to evaluate the identifying performance of VFI. The age-standardized prevalence of dyslipidemia was 29.80% and 26.01% in male and female, respectively. Increasing VFI quartiles were significantly positively related to the risk of dyslipidemia and its components (P_{for trend} < 0.01). The adjusted ORs (95% CIs) for per 1-SD increase in VFI were 2.11 (2.02-2.20) and 1.52 (1.47-1.56) in male and female, respectively, and dose-response relationships were observed in both genders (P_{for nonlinearity} < 0.01). In addition, area under the curves (AUCs) in male (0.697) was larger than in female (0.655) (P < 0.05). VFI was significantly positively related to the risk of dyslipidemia and its components, and the risk was shown to be more prominent in male. Meanwhile, dose-response relationships were observed in both genders. Furthermore, VFI might be a relatively effective marker for identifying dyslipidemia in male, but not in female.

Obesity induction in hamster that mimics the human clinical condition

Although obesity is well established in hamsters, studies using diets with high levels of simple carbohydrate associated with lipids are necessary to assess the impact of this type of food in the body. In this study a high sugar and butter diet (HSB) and high temperature were employed towards this end. Obesity was successfully induced at a temperature of 30.3°C to 30.9°C after 38 days feeding the animals an HSB diet. It was shown that although diet is important for the induction of obesity, temperature is also essential because at a temperature slightly below the one required, obesity was not induced, even when the animals were fed for a longer period (150 days).The obese clinical condition was accompanied by biochemical and hematological changes, as increased cholesterol and triglyceride levels and increased leukocyte numbers, similar to alterations observed in obese humans. Furthermore, it was demonstrated that increasing the intake of simple carbohydrates associated with lipids provided evidence of inflammation in obese animals.

Triglycerides to high-density lipoprotein-cholesterol ratio, glycemic control and cardiovascular risk in obese patients with type 2 diabetes

PURPOSE OF REVIEW

This article provides an update on the role of the triglyceride to high-density lipoprotein-cholesterol (triglyceride/HDL-C) ratio in the setting of obesity-related insulin resistance and type 2 diabetes mellitus.

RECENT FINDINGS

Insulin resistance and type 2 diabetes mellitus are well-established risk factors for cardiovascular diseases, and are commonly associated with metabolic abnormalities such as hypertriglyceridemia, low HDL-C and presence of small, dense low-dense lipoprotein (LDL) particles. Mounting evidence suggests that the triglyceride/HDL-C ratio is a marker of insulin resistance, although this relationship might vary as a function of ethnicity and sex. The triglyceride/HDL-C ratio has also been shown to correlate with other atherogenic lipid measurements, such as triglyceride-rich lipoproteins, remnant cholesterol and small dense LDL particles. Recent epidemiologic studies have shown that the triglyceride/HDL-C ratio associates with cardiovascular risk, mainly because of its association with insulin resistance. Finally, triglyceride/HDL-C can also be a marker of glycemic control, especially in obese patients with type 2 diabetes mellitus.

SUMMARY

The triglyceride/HDL-C integrates information on triglyceride-rich lipoproteins, insulin resistance and glycemic control. Future studies may better define its specific clinical role.

Androgen deficiency and mitochondrial dysfunction: implications for fatigue, muscle dysfunction, insulin resistance, diabetes, and cardiovascular disease

Among the major physiological functions of steroid hormones is regulation of carbohydrate, fat, and protein metabolism. Mitochondria, through oxidative phosphorylation, play a critical role in modulating a host of complex cellular metabolic pathways to produce chemical energy to meet the metabolic demand for cellular function. Thus, androgens may regulate cellular metabolism and energy production by increased mitochondrial numbers, activation of respiratory chain components, and increased transcription of mitochondrial-encoded respiratory chain genes that code for enzymes responsible for oxidative phosphorylation. Androgen deficiency is associated with increased insulin resistance, type 2 diabetes (T2DM), metabolic syndrome, obesity, and increased overall mortality. One common link among all these pathologies is mitochondrial dysfunction. Contemporary evidence exists suggesting that testosterone deficiency (TD) contributes to mitochondrial dysfunction, including structural alterations and reduced expression and activities of metabolic enzymes. Here, we postulate that TD contributes to symptoms of fatigue, insulin resistance, T2DM, cardiovascular risk, and metabolic syndrome through a common mechanism involving impairment of mitochondrial function.

Adiponectin and Insulin in Gray Seals during Suckling and Fasting: Relationship with Nutritional State and Body Mass during Nursing in Mothers and Pups

Animals that fast during breeding and/or development, such as phocids, must regulate energy balance carefully to maximize reproductive fitness and survival probability. Adiponectin, produced by adipose tissue, contributes to metabolic regulation by modulating sensitivity to insulin, increasing fatty acid oxidation by liver and muscle, and promoting adipogenesis and lipid storage in fat tissue. We tested the hypotheses that (1) circulating adiponectin, insulin, or relative adiponectin gene expression is related to nutritional state, body mass, and mass gain in wild gray seal pups; (2) plasma adiponectin or insulin is related to maternal lactation duration, body mass, percentage milk fat, or free fatty acid (FFA) concentration; and (3) plasma adiponectin and insulin are correlated with circulating FFA in females and pups. In pups, plasma adiponectin decreased during suckling (linear mixed-effects model [LME]: T = 4.49; P < 0.001) and the early postweaning fast (LME: T = 3.39; P = 0.004). In contrast, their blubber adiponectin gene expression was higher during the early postweaning fast than early in suckling (LME: T = 2.11; P = 0.046). Insulin levels were significantly higher in early (LME: T = 3.52; P = 0.004) and late (LME: T = 6.99; P < 0.001) suckling than in fasting and, given the effect of nutritional state, were also positively related to body mass (LME: T = 3.58; P = 0.004). Adiponectin and insulin levels did not change during lactation and were unrelated to milk FFA or percentage milk fat in adult females. Our data suggest that adiponectin, in conjunction with insulin, may facilitate fat storage in seals and is likely to be particularly important in the development of blubber reserves in pups.

Diabetic dyslipidemia

Diabetic dyslipidemia is characterized by elevated fasting and postprandial triglycerides, low HDL-cholesterol, elevated LDL-cholesterol and the predominance of small dense LDL particles. These lipid changes represent the major link between diabetes and the increased cardiovascular risk of diabetic patients. The underlying pathophysiology is only partially understood. Alterations of insulin sensitive pathways, increased concentrations of free fatty acids and low grade inflammation all play a role and result in an overproduction and decreased catabolism of triglyceride rich lipoproteins of intestinal and hepatic origin. The observed changes in HDL and LDL are mostly sequence to this. Lifestyle modification and glucose control may improve the lipid profile but statin therapy mediates the biggest benefit with respect to cardiovascular risk reduction. Therefore most diabetic patients should receive statin therapy. The role of other lipid lowering drugs, such as ezetimibe, fibrates, omega-3 fatty acids, niacin and bile acid sequestrants is less well defined as they are characterized by largely negative outcome trials. This review examines the pathophysiology of diabetic dyslipidemia and its relationship to cardiovascular diseases. Management approaches will also be discussed.

Fatty acid sources and their fluxes as they contribute to plasma triglyceride concentrations and fatty liver in humans

PURPOSE OF REVIEW

Different sources of fatty acids (FA) used for VLDL-triglyceride synthesis include dietary FA that clear to the liver via chylomicron uptake, FA synthesized de novo in the liver from carbohydrates, nonesterified fatty acids derived from adipose tissue, nonesterified fatty acids derived from the spillover of chylomicron-triglyceride in the fasted and fed states, and FA stored in liver lipid droplets.

RECENT FINDINGS

Data have amassed on the contributions of each of these sources to liver-triglyceride accrual, VLDL-triglyceride synthesis, and hypertriglyceridemia. Discussed here is the timing of use of FA from each of these sources for synthesis of VLDL-triglyceride. Secondly, as all of these FA sources have been shown to contribute significantly to nonalcoholic fatty liver disease (NAFLD), data are presented demonstrating how poor handling of FA and glucose in the periphery can contribute to NAFLD. Lastly, we highlight how the stress of excess FA availability on the liver can be corrected by reduction of dietary intake of sugars and fats, weight loss, and increased physical activity.

SUMMARY

A better understanding of how lifestyle factors improve FA flux will aid in the development of improved treatments for the devastating condition of NAFLD.

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.

Effect of sex hormones on plasma phospholipid fatty acid composition in intact rats and rats with bilaterally occluded carotid arteries

The effects of 8-days treatment with 17alpha-estradiol (33.3 microg/kg) and progesterone (1.7 mg/kg) on plasma lipids and fatty acid composition of plasma phospholipids were examined in intact (INT) and bilaterally common carotid arteries occluded (BCO) male Wistar rats. Significant decrease of triglyceride level was found in BCO rats after the estradiol treatment. Both hormones elevated proportion of 18:1n-7 fatty acid in INT, but they failed to have such an effect in BCO. Estradiol increased 22:5n-3 and total n-3 polyunsaturated fatty acids (PUFA) in intact, and decreased 18:2n-6 in BCO rats. Significantly lower level of total n-3 was found in progesterone-treated than in estradiol-treated BCO rats. Given that n-3 PUFA have many beneficial effects on cell and tissue function, while n-6 PUFA have mostly the opposite effects, estradiol, rather than progesterone, was seen to improve plasma lipids and phospholipids FA profiles in INT and BCO animals. Estradiol significantly elevated the estimated activity of delta9-desaturases and progesterone of delta5-desaturase in BCO group, with no effects in INT rats.

Relationship between fatty acids and the endocrine and neuroendocrine system

Significant interactions exist between fatty acids and the endocrine system. Dietary fatty acids alter both hormone and neuropeptide concentrations and also their receptors. In addition, hormones affect the metabolism of fatty acids and the fatty acid composition of tissue lipids. The principal hormones involved in lipid metabolism are insulin, glucagon, catecholamines, cortisol and growth hormone. The concentrations of these hormones are altered in chronic degenerative conditions such as diabetes and cardiovascular disease, which in turn leads to alterations in tissue lipids. Lipogenesis and lipolysis, which modulate fatty acid concentrations in plasma and tissues, are under hormonal control. Neuropeptides are also involved in lipid metabolism in brain and other tissues. Polyunsaturated fatty acids are also precursors for eicosanoids including prostaglandins, leucotrienes, and thromboxanes, which have hormone-like activities. Fatty acids in turn affect the endocrine system. Saturated and trans fatty acids decrease insulin concentration leading to insulin resistance. In contrast, polyunsaturated fatty acids increase plasma insulin concentration and decrease insulin resistance. In humans, omega3 polyunsaturated fatty acids alter the levels of opioid peptides in plasma. Free fatty acids have been reported to inhibit glucagon release. Fatty acids also affect receptors for hormones and neuropeptides.

Genetic variation in APOJ, LPL, and TNFRSF10B affects plasma fatty acid distribution in Alaskan Eskimos

BACKGROUND

Alterations in plasma fatty acid distribution are linked to metabolic abnormalities related to type 2 diabetes and cardiovascular disease.

OBJECTIVE

The aim of this study was to investigate genetic factors influencing plasma fatty acid distribution in Alaskan Eskimos from the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) study.

DESIGN

Fatty acids in plasma were measured by gas chromatography in 761 related individuals (>35 y of age).

RESULTS

Quantitative genetic analyses showed that fatty acid distribution is significantly heritable (P < 0.001), with heritabilities ranging from 0.33 to 0.55. A genome-wide scan for plasma fatty acids identified a 20-cM region on chromosome 8 (p12-p21) with a quantitative trait locus for monounsaturated fatty acids (logarithm of odds score = 3.8). The same region had a quantitative trait locus for polyunsaturated fatty acids (logarithm of odds score = 2.6). We genotyped single nucleotide polymorphisms (SNPs) in candidate genes in 8p12-p21 and found a significant association between fatty acids and SNPs in apolipoprotein J (APOJ), lipoprotein lipase (LPL), macrophage scavenger receptor 1 (MSR1), and tumor necrosis factor receptor superfamily member 10b (TNFRSF10B). A Bayesian quantitative trait nucleotide analysis based on a measured genotype model showed that SNPs in LPL, TNFRSF10B, and APOJ had strong statistical evidence of a functional effect (posterior probability > or =75%) on plasma fatty acid distribution.

CONCLUSIONS

The results indicate that there is strong genetic influence on plasma fatty acid distribution and that genetic variation in APOJ, LPL, and TNFRSF10B may play a role. The GOCADAN study was registered at www.clinicaltrials.gov as NCT00006192.

O papel dos hormônios leptina e grelina na gênese da obesidade

A prevalência da obesidade está aumentando e estudos prospectivos mostram que, em 2025, o Brasil será o quinto país do mundo a apresentar problemas de obesidade em sua população. A etiologia da obesidade não é de fácil identificação, uma vez que a mesma é caracterizada como uma doença multifatorial, ou seja, diversos fatores estão envolvidos em sua gênese, incluindo fatores genéticos, psicológicos, metabólicos e ambientais. Pesquisas recentes na área de metabolismo mostram que o adipócito é capaz de sintetizar várias substâncias e, diferentemente do que se supunha anteriormente, o tecido adiposo não é apenas um sítio de armazenamento de triglicérides, é hoje considerado um órgão endócrino. Dentre as diversas substâncias sintetizadas pelo adipócito, destacam-se a adiponectina, a angiotensina e a leptina. A leptina é um petídeo que desempenha importante papel na regulação da ingestão alimentar e no gasto energético, gerando um aumento na queima de energia e diminuindo a ingestão alimentar. Além dos avanços no estudo da célula adiposa, um novo hormôrnio relacionado ao metabolismo foi descoberto recentemente, a grelina. A grelina é um peptídeo produzido nas células do estômago, e está diretamente envolvida na regulação do balanço energético a curto prazo. Assim, este artigo abordará o papel da leptina e da grelina no controle do peso corporal e as limitações que ainda existem para tratar a obesidade em humanos.

Free fatty acids are associated with obesity, insulin resistance, and atherosclerosis in renal transplant recipients

BACKGROUND

Insulin resistance (IR) may be implicated in the pathogenesis of atherosclerosis in renal transplant recipients (RTRs) and be contributed to, in part, by free fatty acids (FFAs), produced in excess in centrally obese individuals. The aim of this study was to determine the prevalence of IR and the relationships between FFAs, central obesity, and atherosclerosis in a cohort of prevalent RTRs.

METHODS

Observational data were collected on 85 RTRs (mean age 54 years; 49% male, 87% Caucasian). Fasting serum was analyzed for FFAs, glucose, and insulin; IR was calculated using the homeostasis model assessment (HOMA-IR) score. Vascular structure was assessed by carotid intima-media thickness (IMT) measurement. Linear regression analyses were performed to determine the factors associated with IR and atherosclerosis.

RESULTS

IR occurred in 75% of RTRs, and FFA levels were independently associated with its occurrence (beta: -0.55, 95% CI: -1.02 to -0.07, P = 0.02). Other variables independently associated with IR were male sex, body mass index, central obesity, diabetes, systolic blood pressure and corticosteroid use. There was a significant correlation between FFA levels and IMT (r = 0.3, P=0.01). On multivariate analysis, IMT correlated with elevated FFA (beta: 0.07, 95% CI: 0.02-0.12, P = 0.007), diabetes mellitus (P = 0.05), older age (P < 0.002), and a body mass index >25 kg/m (P = 0.002).

CONCLUSIONS

FFAs are associated with the development of IR and may be involved in the pathogenesis of atherosclerosis in RTRs. Additional studies are required to explore these associations further before considering whether an interventional trial aimed at lowering FFA would be a worthwhile undertaking.

The adrenergic control of hepatic glucose and FFA metabolism in rainbow trout (Oncorhynchus mykiss): increased sensitivity to adrenergic stimulation with fasting

The adrenergic control of glucose and FFA release was studied in hepatocytes of rainbow trout (Oncorhynchus mykiss), which were either normally fed or fasted for 3 weeks. Isolated hepatocytes were incubated with adrenaline, noradrenaline, or isoprenaline (nonselective beta-agonist). Identification of the hepatic beta-adrenoceptor was combined with quantification of the difference in its affinity for adrenaline and noradrenaline. To identify the beta-adrenoceptor subtype, isoprenaline incubations were combined with atenolol (selective beta(1)-antagonist) or ICI 118,551 (selective beta2-antagonist). Stimulation of the beta-adrenoceptor resulted in mobilisation of glucose, which was inhibited by ICI 118,551 thus pointing to a beta2-subtype. The affinity of the beta2-adrenoceptor for isoprenaline and adrenaline (beta2-values of 8.3 and 7.9) was clearly higher than for noradrenaline (beta2-value of 6.5). This indicates that at physiological concentrations beta2-adrenoceptors in trout are mainly stimulated by adrenaline and not by noradrenaline. A significant effect of beta-adrenoceptor stimulation on the FFA release was also found, although only at high concentrations (i.e., 10(-6) and 10(-5)M). Again the beta2-adrenoceptor appeared to mediate the stimulation of hepatic FFA release. Upon fasting, both the basal glucose and FFA release were strongly decreased. The ratio between glucose and FFA release decreased from 15.4 to 4.3 upon fasting and at this ratio the energy output for both metabolites became equal. The mobilisation of FFA upon adrenergic stimulation was relatively conserved, namely -35% upon fasting, as opposed to -89% in mobilisation of glucose. This indicates that upon fasting FFA gain importance in hepatic metabolism. The hepatic sensitivity to adrenergic stimulation is enhanced upon fasting, as indicated by an increased beta2-value from 8.3 to 8.9.

Statin use in the metabolic syndrome

The metabolic syndrome is a condition associated with obesity, insulin resistance, hypertension, dyslipidemia, hypercoagulability, and chronic inflammation, all of which increase the risk of cardiovascular disease (CVD). The Third National Cholesterol Education Program Adult Treatment Panel extensively discussed the metabolic syndrome because it is a major health issue in the United States due to the national epidemic of obesity. Statins cause significant CVD risk reduction in patients with the metabolic syndrome by alterations in lipid levels and possibly by decreasing inflammation. Because of the increased CVD risk associated with the metabolic syndrome and extensive clinical trial evidence documenting reduction of CVD risk with statin treatment, all patients with the metabolic syndrome should be evaluated as candidates for statin treatment as part of a multidisciplinary approach to reduce CVD risk.

Rational Design of a Chromo- and Fluorogenic Hybrid Chemosensor Material for the Detection of Long-Chain Carboxylates

A strategy for the rational design of a new optical sensor material for the selective recognition of long-chain carboxylates in water is presented. The approach relies on the combination of structure-property relationships to single out the optimal molecular sensor unit and the tuning of the sensing characteristics of an inorganic support material. A spacer-substituted 7-urea-phenoxazin-3-one was employed as the signaling moiety and a mesoporous trimethylsilylated UVM-7 (MCM-41 type) material served as the solid support. The sensor material shows the advantageous features of both modules that is absorption and emission in the visible spectral range, a fluorescence red-shift and enhancement upon analyte coordination, and the amplification of noncovalent (binding) and hydrogen-bonding (recognition) interactions in the detection event. Besides these basic results that are related to the design and performance of the sensor material, the paper discusses general aspects of amido-substituted phenoxazinone photophysics and addresses some general features of molecular anion recognition chemistry in aqueous vs nonaqueous media, utilizing steady-state and time-resolved optical as well as NMR spectroscopies. Detailed studies on potentially competing biochemical species and a first access to the schematic model of the response of the sensor material as obtained by a combination of fluorescence lifetime distribution analysis and Langmuir-type fitting of the gross binding constants complement the key issues of the paper.

In vivo regulation of plasma free fatty acids in insulin resistance

Elevated plasma free fatty acid (FFA) concentrations as seen in obesity, insulin resistance, and type 2 diabetes are partly caused by impaired inhibition of intracellular lipolysis in adipose tissue, and this is considered to be part of the insulin resistance syndrome (IRS). Based on predicted insulin resistance at the level of intracellular lipolysis, patients with the IRS would loose weight by disinhibited lipolysis. Since this is not the case in clinical practice, impaired stimulation of intracellular lipolysis must also play a role. We studied acute plasma FFA changes, representing stimulation and inhibition of intracellular adipose tissue lipolysis, in obese patients with IRS and in healthy controls. Thirteen insulin-resistant (IR) subjects (7 men and 6 women) and 10 controls (6 men and 4 women) underwent a mental stress test (20 minutes) preceded by 60 minutes of rest. After mental stress, an oral glucose tolerance test (OGTT) was performed. Baseline FFA levels were higher in IR patients compared to controls (0.59 +/- 0.06 and 0.31 +/- 0.06 mmol/L, respectively; P =.004). During the 20 minutes of mental stress, FFAs increased significantly in IR subjects from 0.55 +/- 0.07 to 0.67 +/- 0.07 mmol/L (P <.001) and from 0.21 +/- 0.04 to 0.36 +/- 0.07 mmol/L in controls (P =.001). Although the absolute change of plasma FFA was not different, the relative increase was lower in IR subjects (28% +/- 7%) compared to controls (89 +/- 24%; P =.02). Despite the more pronounced mean maximal insulin concentration during the OGTT in IR subjects compared to controls (600.0 +/- 126.6 pmol/L and 208.1 +/- 30.0 pmol/L, respectively), the relative decrease of FFAs was lower in IR subjects (11% +/- 5% v 36% +/- 11% in controls after 30 minutes; P =.04). In conclusion, our study shows impaired acute responses of plasma FFAs upon stimulation by mental stress and inhibition by endogenous insulin in insulin resistance in vivo. The presence of both defects helps to understand weight maintenance in insulin resistance.

Lipid metabolism in hepatic steatosis

Hepatic steatosis is a consequence of both obesity and ethanol use. Nonalcoholic steatosis (NASH) resemble alcoholic steatosis and steatohepatitis. Both exhibit increased hepatocellular triglycerides(TG), reflecting an increase in long chain fatty acids (LCFA). LCFA enter cells by both facilitated transport and passive diffusion. A driving force for both is the plasma unbound LCFA concentration ([LCFAu]). In both obese rodents and obese patients, adipocyte LCFA uptake via both facilitated transport and diffusion is increased. However, the LCFA uptake Vmax in hepatocytes is not increased in obese animals. Nevertheless, total LCFA uptake in obese rodents is increased ~3-fold, reflecting increased plasma LCFA concentrations. With advancing obesity, resistance to the antilipolytic effects of insulin results in increased lipolysis within the omental fat depot, a consequent further rise in portal venous LCFA, and an even greater rise in portal [LCFAu]. This causes a further increase in hepatocellular LCFA uptake, increased intracellular generation of reactive oxygen species (ROS), and transition from simple steatosis to NASH. By contrast, in rodent hepatocytes and in human hepatoma cell lines, ethanol up-regulates the LCFA uptake Vmax. Consequently, although plasma LCFA are unaltered, hepatocellular LCFA uptake in ethanol-fed rats is also increased~3-fold, leading to increased ROS generation and evolution of alcoholic hepatitis. Thus, while increased hepatic LCFA uptake contributes to the pathogenesis of both NASH and alcoholic hepatitis,the underlying mechanisms differ. Recognizing these mechanistic differences is important in developing strategies for both prevention and treatment of these conditions.

Impairment of Hepatic Microcirculation in Fatty Liver

Fatty liver or hepatic steatosis, which is the result of the abnormal accumulation of triacylglycerol within the cytoplasm of hepatocytes, is a common histological finding in human liver biopsy specimens that is attributed to the effects of alcohol excess, obesity, diabetes, or drugs. There is a general consensus that fatty liver compromises hepatic microcirculation, the common exchange network upon which hepatic arterial and portal inflows converge, regardless of underlying etiology. A significant reduction in hepatic microcirculation has been observed in human fatty donor livers and in experimental models of hepatic steatosis. There is an inverse correlation between the degree of fat infiltration and both total hepatic blood flow and flow in microcirculation. Fatty accumulation in the cytoplasm of the hepatocytes is associated with an increase in the cell volume that reduces the size of the hepatic sinusoid space by 50% compared with a normal liver and may result in partial or complete obstruction of the hepatic sinusoid space. As a result of impaired hepatic microcirculation, the hepatocytes of the fatty liver have reduced tolerance against ischemia-reperfusion injury, which affects about 25% of the donors for liver transplantation because severe steatosis is associated with a high risk of primary nonfunction after liver transplantation.

Gender differences in diurnal triglyceridemia in lean and overweight subjects

AIMS

Increased fasting and postprandial triglyceridemia is one of the cardiovascular risk factors for patients with insulin resistance. Since triglyceride (TG) metabolism largely depends on gender, we have investigated diurnal TG changes in patients with and without overweight, focusing on gender differences.

METHODS

Twenty-two males and 22 females with overweight (mean body mass index (BMI) 28.0+/-2.3 kg/m2) measured capillary TG concentrations at six fixed time points on three different days. Diurnal TG profiles were calculated as area under the capillary TG curves (TGc-AUCs). The control group consisted of 24 males and 21 females who were not overweight (mean BMI 22.4+/-1.5 kg/m2). Biochemical and anthropometric parameters associated with insulin resistance were measured.

RESULTS

Lean males and lean females had comparable fasting insulin levels (6.9+/-2.6 and 8.1+/-4.7 mU/l, respectively), but females had a more favorable fasting lipoprotein profile when compared to males. Diurnal TG profiles were lower in lean females than in lean males (16.9+/-4.3 vs 20.3+/-5.7 mMh, respectively, P<0.05). Overweight males and females had comparable fasting insulin levels (10.3+/-3.4 and 12.1+/-4.9 mU/l, respectively), which were higher than in lean subjects. Overweight females also had a more favorable fasting lipoprotein profile compared to overweight males. Diurnal TG profiles were similar in overweight females and overweight males (31.1+/-15.6 and 32.9+/-13.2 mMh, respectively). Stepwise multiple regression analysis showed that in both males and females, waist circumference was the strongest determinant of diurnal TG profiles when fasting TG concentrations were excluded from the model (R2=0.49 for males and R2=0.33 for females). These results suggest that overweight resulted in a 'male diurnal TG profile' in females due to abdominal fat accumulation.

CONCLUSION

Insulin resistance in overweight subjects partly mitigates the gender differences of fasting and postprandial TG metabolism. The significant positive association between diurnal triglyceridemia and waist circumference supports the view that especially abdominal fat associated with insulin resistance enhances postprandial lipemia.

Acylation stimulating protein (ASP) acute effects on postprandial lipemia and food intake in rodents

BACKGROUND

In vitro studies have shown that acylation stimulating protein (ASP) stimulates triglyceride (TG) synthesis and storage in adipocytes. We have previously demonstrated that intraperitoneal (i.p.) injection of ASP in C57BL/6J mice accelerated TG clearance following an orally-administered fat load as well as reducing postprandial glucose levels.

RESULTS

In the present study, we first examined the effect of i.p. and intracerebroventricular (i.c.v.) injection of ASP on food intake in Sprague-Dawley rats. Intraperitoneal injection resulted in a short-term increase in food intake (maximum increase 29.3% within the first hour, P<0.025) decreasing thereafter as compared to vehicle alone. i.c.v. Administration of a comparable dose of ASP resulted in a similar but delayed increase in food intake with a maximum at 2-4 h, suggesting that the actions of ASP are peripherally mediated. However, there was no significant difference in 24 h food intake with either i.p. or i.c.v. injection. We also examined the effects of ASP on TG clearance in two obese mouse strains with different metabolic profiles: ob/ob (C57BL/6J-Lep(ob)) and db/db (C57BLKS/J-Lepr(db)). In a crossover design, the response to an oral fat load was determined with and without i.p. injection of exogenous ASP. In ob/ob mice, there was a 44% greater clearance of postprandial TG (area under the curve (AUC)=245+/-49 control vs 138+/-43 mg/dl h with ASP; P<0.05 by RM ANOVA). The db/db mice showed a greater response, with a 62% decrease in postprandial TG (AUC=4080+/-1489 control vs 1540+/-719 mg/dl h with ASP; P=0.004 by RM ANOVA). In addition there were decreases in postprandial glucose and non-esterified fatty acid (NEFA) levels in response to ASP.

CONCLUSION

These results are the first to report that ASP can increase food intake in rats and also enhance postprandial TG clearance in obese animals. These data therefore support previous in vitro evidence pointing to ASP as a regulator of lipid metabolism.

Visceral obesity and metabolic syndrome

There is increasing evidence for the existence of a condition consisting of a cluster of metabolic disorders which include insulin resistance, alterations in glucose and lipid metabolism, increased blood pressure and visceral obesity. The metabolic syndrome is now the favoured definition of the cluster. Each single component of the cluster increases the cardiovascular risk, but the combination of factors is much more important. Insulin resistance is the most frequently associated factor to the singular components of the syndrome: most authors believe that it may be the common aetiological factor. However, visceral obesity seems to be the main driving factor by means of the increased production of free fatty acids whose activity, in turn, might interfere with the action of insulin. Some questions exist about the syndrome because of the frequent lack in the cluster of one of the factors. This does not mean that the missing factor does not belong to the syndrome, but only that it is not yet clinically evident. Weight gain has been shown to be a strong predictor of the metabolic syndrome. This aspect gives strength to treatment and prevention because it means that losing weight or stopping weight increase might reduce the risk of a future appearance of a factor that is still not evident. Interventions to treat visceral obesity by means of losing weight seem to be the most efficacious way to treat the metabolic syndrome thus improving the most widespread cardiovascular risk factor in western countries.

Fat cell metabolism: insulin, fatty acids, and renin

Risk factors contributing to the potential inter-relationship between obesity and hypertension include insulin, fatty acids, and angiotensin II. All of these mediators are either produced by or act on adipocytes, influence fat cell metabolism, and have effects on the cardiovascular system. Moreover, these three mediators have several potential sites for positive feedback interaction, thus exacerbating the influence of any single risk factor. The purpose of this review is to highlight recent advances in our understanding of the influence of insulin, fatty acids, and angiotensin II on fat cell metabolism. Special emphasis is placed on potential adipose-related mechanisms of these factors, which would predictably elevate blood pressure. Given the prevalence of obesity and hypertension in the American population, delineation of potential pharmacologic targets that would influence both of these disease states is of primary importance to the successful treatment of these diseases of the metabolic syndrome X.

Relationship between fatty acids and the endocrine system

Significant interactions exist between fatty acids and the endocrine system. Hormones affect the metabolism of fatty acids and the fatty acid composition of tissue lipids. The principal hormones involved in lipid metabolism are insulin, glucagon, catecholamines, cortisol and growth hormone. The concentrations of these hormones are altered in chronic degenerative conditions such as diabetes and cardiovascular disease, which in turn lead to alterations in tissue lipids. Lipogenesis and lipolysis, which modulate fatty acid concentrations in plasma and tissues, are under hormonal control. Neuropeptides are involved in lipid metabolism in brain and other tissues. Polyunsaturated fatty acids (PUFA) are also precursors for eicosanoids including prostaglandins, leukotrienes, and thromboxanes, which have hormone-like activities. Fatty acids in turn alter both hormone and neuropeptide concentrations and their receptors. Saturated and trans fatty acids (TFA) decrease insulin concentration leading to insulin resistance. In contrast, PUFA increase plasma insulin concentration and decrease insulin resistance. In humans, omega-3 PUFA alter the levels of opioid peptides in plasma.