FFAs: do they play a role in vascular disease in the insulin resistance syndrome?

Endothelial autophagy-related gene 7 contributes to high fat diet-induced obesity

OBJECTIVE

Obesity-associated metabolic dysfunction is a major public health concern worldwide. Endothelial dysfunction is a hallmark of metabolic dysfunction, and endothelial cells affect metabolic functions. Because autophagy-related gene 7 (ATG7) is involved in various cellular physiology, we investigated the roles of endothelial cell-ATG7 (EC-ATG7) on high-fat diet-induced obesity and its related metabolic dysfunction.

METHODS

We generated an endothelial-specific Atg7 knock-out mouse by breeding Atg7flox/flox mouse with the Chd5-Cre mouse, and investigated the metabolic phenotypes associated with high-fat diet (HFD)-induced obesity. Body weight, food intake, glucose tolerance, insulin sensitivity, and liver fat accumulation were measured in endothelial Atg7 deficient (Atg7ΔEnd) and control mice (Atg7f/f). Adipose tissue inflammation was assessed by measuring the expression of pro-inflammatory genes. Furthermore, we performed indirect calorimetry and examined the insulin signaling pathway molecules.

RESULTS

We found that deletion of EC-Atg7 ameliorated HFD-induced weight gain, fatty liver, and adipocyte hypertrophy and inflammatory response in adipose tissue, and improved insulin sensitivity without changing glucose tolerance. These metabolic effects seem to be due to the reduced food intake because there were no differences in energy expenditure, energy excretion to feces, and physical activity. Interestingly, the deletion of EC-Atg7 protected from HFD-induced vascular rarefaction, and the knock-down of Atg7 in endothelial cells protected from fatty acid-induced cell death.

CONCLUSIONS

Our results suggest that EC-Atg7 deletion ameliorates HFD-induced obesity and its related metabolic dysfunction, such as insulin resistance and fatty liver by attenuating appetite and vascular rarefaction. The EC-Atg7 deletion may protect the endothelial cells from lipotoxicity and impaired angiogenesis, which preserves the endothelial function in metabolic tissues. These findings may have implications for developing new therapeutic strategies for preventing and treating obesity and its associated health risks.

Non-esterified fatty acids and risk of peripheral artery disease in older adults: The cardiovascular health study

BACKGROUND AND AIMS

Non-esterified fatty acids have been implicated in the pathogenesis of diabetes and cardiovascular disease. No longitudinal study has assessed their effects on peripheral artery disease (PAD). We determined the relationships between NEFAs and incident clinical PAD and abnormal ankle-brachial index (ABI) in a population-based cohort of older persons.

METHODS

We evaluated 4575 community living participants aged >65 years who underwent measurement of circulating NEFAs in fasting specimens and ABI in 1992-1993. Participants were assessed annually for clinical PAD until 2015 and underwent repeat ABI in 1998-1999. We used Cox proportional hazards regression to model the associations between NEFAs and risk of clinical PAD and logistic regression to model the associations of NEFAs with incident abnormal ABI.

RESULTS

Mean age was 74.8 years, 59% were female, and 17% were Black. NEFAs were associated with higher risk of clinical PAD in unadjusted and adjusted models. The adjusted hazard ratios for incident clinical PAD were 1.51 (95%CI = 1.06-2.13, p = 0.02) across extreme tertiles, and 1.14 (95%CI = 0.99-1.31, p = 0.08) per standard deviation higher NEFA. The corresponding odds ratios for abnormal ABI were 0.95 (95%CI = 0.69-1.32, p = 0.76) across extreme tertiles, and 1.03 (95%CI = 0.89-1.20, p = 0.68) per standard deviation higher NEFA. Relationships appeared similar irrespective of sex, race, or pre-existing cardiovascular disease, but were stronger later than earlier in follow-up.

CONCLUSIONS

Higher serum levels of NEFAs are significantly associated with increased likelihood of clinical PAD over long-term follow-up but not with 6-year decline in ABI. NEFAs may offer a potential target for intervention against clinical PAD.

Nonesterified fatty acids, cognitive decline, and dementia

PURPOSE OF REVIEW

Dementia is rapidly growing as sources of morbidity and mortality as the US population ages, but its pathophysiology remains poorly understood. As a result, no disease-modifying treatments currently exist. We review the evidence that nonesterified fatty acids may play a key role in this condition.

RECENT FINDINGS

Nonesterified fatty acids appear to influence several pathways leading to dementia. In addition to their vascular effects, these moieties cross the blood-brain barrier, where they are toxic to several cell types. They may also influence insulin metabolism in the brain directly and indirectly, and some drugs that lower circulating levels appear to slow cognitive decline and brain atrophy in diabetes.

SUMMARY

Nonesterified fatty acids may contribute to dementia, much as they do to diabetes and cardiovascular disease. Several therapeutic agents lower circulating levels of nonesterified fatty acids and should be tested for their potential preventive effects on cognitive decline in healthy populations before irreversible neuronal attrition occurs.

Increased maternal C1q/TNF-related protein-1 (CTRP-1) serum levels in pregnancies with preeclampsia

Objective: Metabolic changes and inflammation are involved in the pathogenesis of preeclampsia. Complement C1q tumor necrosis factor-related protein-1 (CTRP-1) is a pleiotropic molecule that possesses insulin-sensitizing effects and is also involved in lipid metabolism and inflammatory responses. The aim of the study was to investigate CTRP-1 levels in pregnancies with preeclampsia.Material and methods: Serum concentrations of CTRP-1 were measured in 29 pregnant women with early-onset preeclampsia (EOPE), 24 pregnant women with late-onset preeclampsia (LOPE), and 26 women with uncomplicated pregnancies using an enzyme-linked immunosorbent assay method.Results: Patients with both EOPE and LOPE had significantly higher serum concentrations of CTRP-1 compared to the healthy controls (p < .001). However, no significant difference was found between the EOPE and LOPE groups regarding CTRP-1 levels (p = 1.000). Correlation analysis showed that CTRP-1 levels were positively correlated with systolic blood pressure (p < .001), diastolic blood pressure (p < .001), and mean UtA PI (p < .001) but negatively correlated with gestational age at delivery (p = .001) and birth weight (p < .001).Conclusions: Serum CTRP-1 levels were significantly higher in patients with both EOPE and LOPE than in healthy pregnant women.

Lipotoxicity as a trigger factor of renal disease

In the last few decades, rapid changes in lifestyle have led to an alarming increase in the prevalence of obesity and obesity-associated complications. Obese patients are at increased risk of developing hypertension, heart disease, insulin resistance, dyslipidemia, type 2 diabetes and kidney disease. The surplus of calories is normally stored as triglycerides in adipose tissue. However, excess lipids can also accumulate ectopically in other organs, including the kidney, contributing to their damage through toxic processes named lipotoxicity. The kidney is negatively affected by dyslipidemia, lipid accumulation and changes in circulating adipokines that bring about alterations in renal lipid metabolism and promote insulin resistance, generation of reactive oxygen species and endoplasmic reticulum stress, ultimately leading to alterations in the glomerular filtration barrier and renal failure. This review focuses on the pathogenic molecular mechanisms associated with renal lipotoxicity, and presents new insights about potential new therapeutic targets and biomarkers such as microRNAs and long non-coding RNAs, of relevance for the early detection of lipid-associated kidney disease.

Palmitate diet-induced loss of cardiac caveolin-3: a novel mechanism for lipid-induced contractile dysfunction

Obesity is associated with an increased risk of cardiomyopathy, and mechanisms linking the underlying risk and dietary factors are not well understood. We tested the hypothesis that dietary intake of saturated fat increases the levels of sphingolipids, namely ceramide and sphingomyelin in cardiac cell membranes that disrupt caveolae, specialized membrane micro-domains and important for cellular signaling. C57BL/6 mice were fed two high-fat diets: palmitate diet (21% total fat, 47% is palmitate), and MCT diet (21% medium-chain triglycerides, no palmitate). We established that high-palmitate feeding for 12 weeks leads to 40% and 50% increases in ceramide and sphingomyelin, respectively, in cellular membranes. Concomitant with sphingolipid accumulation, we observed a 40% reduction in systolic contractile performance. To explore the relationship of increased sphingolipids with caveolins, we analyzed caveolin protein levels and intracellular localization in isolated cardiomyocytes. In normal cardiomyocytes, caveolin-1 and caveolin-3 co-localize at the plasma membrane and the T-tubule system. However, mice maintained on palmitate lost 80% of caveolin-3, mainly from the T-tubule system. Mice maintained on MCT diet had a 90% reduction in caveolin-1. These data show that caveolin isoforms are sensitive to the lipid environment. These data are further supported by similar findings in human cardiac tissue samples from non-obese, obese, non-obese cardiomyopathic, and obese cardiomyopathic patients. To further elucidate the contractile dysfunction associated with the loss of caveolin-3, we determined the localization of the ryanodine receptor and found lower expression and loss of the striated appearance of this protein. We suggest that palmitate-induced loss of caveolin-3 results in cardiac contractile dysfunction via a defect in calcium-induced calcium release.

FABP4 dynamics in obesity: discrepancies in adipose tissue and liver expression regarding circulating plasma levels

BACKGROUND

FABP4 is predominantly expressed in adipose tissue, and its circulating levels are linked with obesity and a poor atherogenic profile.

OBJECTIVE

In patients with a wide BMI range, we analyze FABP4 expression in adipose and hepatic tissues in the settings of obesity and insulin resistance. Associations between FABP4 expression in adipose tissue and the FABP4 plasma level as well as the main adipogenic and lipolytic genes expressed in adipose tissue were also analyzed.

METHODS

The expression of several lipogenic, lipolytic, PPAR family and FABP family genes was analyzed by real time PCR. FABP4 protein expression in total adipose tissues and its fractions were determined by western blot.

RESULTS

In obesity FABP4 expression was down-regulated (at both mRNA and protein levels), with its levels mainly predicted by ATGL and inversely by the HOMA-IR index. The BMI appeared as the only determinant of the FABP4 variation in both adipose tissue depots. FABP4 plasma levels showed a significant progressive increase according to BMI but no association was detected between FABP4 circulating levels and SAT or VAT FABP4 gene expression. The gene expression of FABP1, FABP4 and FABP5 in hepatic tissue was significantly higher in tissue from the obese IR patients compared to the non-IR group.

CONCLUSION

The inverse pattern in FABP4 expression between adipose and hepatic tissue observed in morbid obese patients, regarding the IR context, suggests that both tissues may act in a balanced manner. These differences may help us to understand the discrepancies between circulating plasma levels and adipose tissue expression in obesity.

Estrogens and selective estrogen receptor modulators regulate gene and protein expression in the mesenteric arteries

Estrogen has both beneficial and detrimental effects on the cardiovascular system. Selective estrogen receptor modulators (SERMs) exhibit partial estrogen agonist/antagonist activity in estrogen target tissues. Gene targets of estrogen and SERMs in the vasculature are not well-known. Thus, the present study tested the hypothesis that estrogens (ethinyl estradiol, estradiol benzoate, and equilin) and SERMs (tamoxifen and raloxifene) cause differential gene and protein expression in the vasculature. DNA microarray and real-time RT-PCR were used to investigate gene expression in the mesenteric arteries of estrogen and SERM treated ovariectomized rats. The genes shown to be differentially expressed included stearoyl-CoA desaturase (SCD), soluble epoxide hydrolase (sEH), secreted frizzled related protein-4 (SFRP-4), insulin-like growth factor-1 (IGF-1), phospholipase A2 group 1B (PLA2-G1B), and fatty acid synthase (FAS). Western blot further confirmed the differential expression of sEH, SFRP-4, FAS, and SCD protein. These results reveal that estrogens and SERMs cause differential gene and protein expression in the mesenteric artery. Consequently, the use of these agents may be associated with a unique profile of functional and structural changes in the mesenteric arterial circulation.

Molecular Model of Plasma PAF Acetylhydrolase-Lipoprotein Association: Insights from the Structure

Plasma platelet-activating factor acetylhydrolase (PAF-AH), also called lipoprotein-associated phospholipase A₂ (Lp-PLA₂), is a group VIIA PLA₂ enzyme that catalyzes the hydrolysis of PAF and certain oxidized phospholipids. Although the role of PAF-AH as a pro- or anti-atherosclerotic enzyme is highly debated, several studies have shown it to be an independent marker of cardiovascular diseases. In humans the majority of plasma PAF-AH is bound to LDL and a smaller portion to HDL; the majority of the enzyme being associated with small dense LDL and VHDL-1 subclasses. Several studies suggest that the anti- or pro-atherosclerotic tendency of PAF-AH might be dependent on the type of lipoprotein it is associated with. Amino acid residues in PAF-AH necessary for binding to LDL and HDL have been identified. However our understanding of the interaction of PAF-AH with LDL and HDL is still incomplete. In this review we present an overview of what is already known about the interaction of PAF-AH with lipoprotein particles, and we pose questions that are yet to be answered. The recently solved crystal structure of PAF-AH, along with functional work done by others is used as a guide to develop a model of interaction of PAF-AH with lipoprotein particles.

The metabolic profile in patients with skin tags

Although skin tags are associated with diabetes mellitus, insulin resistance, hypertension, obesity, atherogenic lipid profile, no data in the literature show that the presence of skin tags is associated with serum high-sensitive C-reactive protein, uric acid, free fatty acid and leptin level. The purpose of this study was to evaluate the frequency of hypertension, dyslipidemia, insulin resistance and obesity in patients with skin tags and to compare patients with skin tags and normal healthy subjects for insulin resistance, serum lipids, insulin, glucose, leptin, high-sensitive C-reactive protein, free fatty acid levels. We evaluated 113 patients with skin tags and 31 healthy subjects. The two groups were compared with respect to BMI, lipid profile, blood pressure, insulin resistance, serum lipids, insulin, glucose, leptin, high-sensitive C-reactive protein, free fatty acid and homeostatic model assessment of insulin resistance (HOMA-IR). Total 53.9 and 33.6% of patients with skin tags were overweight and obese, respectively. The frequency of hypertension 30.1%, dyslipidemia 59.3% and insulin resistance 21.2% were detected. HOMA-IR (P < 0.001) and serum glucose (P < 0.001), insulin (P = 0.002), high-sensitive C-reactive protein (P = 0.001), uric acid (P = 0.001), free fatty acid (P = 0.002), HbA1c (P < 0.001), total cholesterol (P = 0.018), LDL-cholesterol (P = 0.023), and triglyceride levels (P = 0.001) were higher in patients with skin tags than control group. Overweight and/or obesity, dyslipidemia, hypertension, insulin resistance and elevated high-sensitive C-reactive protein are seen in patients with skin tags. Skin tags may be a marker of increased risk of atherosclerosis and cardiovascular disease.

Muscle contraction, but not insulin, increases microvascular blood volume in the presence of free fatty acid-induced insulin resistance

OBJECTIVE

Insulin and contraction each increase muscle microvascular blood volume (MBV) and glucose uptake. Inhibiting nitric oxide synthase blocks insulin's but not contraction's effects. We examined whether contraction could augment the MBV increase seen with physiologic hyperinsulinemia and whether free fatty acid (FFA)-induced insulin resistance differentially affects contraction- versus insulin-mediated increases in MBV.

RESEARCH DESIGN AND METHODS

Rats were fasted overnight. Plasma FFAs were increased by intralipid/heparin infusion (3 h), insulin was increased with a euglycemic clamp (3 mU x min(-1) x kg(-1)), and hindlimb muscle contraction was electrically stimulated. Muscle MBV was measured using contrast-enhanced ultrasound. Insulin transport into muscle was measured using (125)I-insulin. BQ-123 (0.4 mg/h) was used to block the endothelin-1 (ET-1) receptor A.

RESULTS

Superimposing contraction on physiologic hyperinsulinemia increased MBV within 10 min by 37 and 67% for 0.1 or 1 Hz, respectively (P < 0.01). FFA elevation alone did not affect MBV, whereas 0.1 Hz stimulation doubled MBV (P < 0.05) and increased muscle insulin uptake (P < 0.05) despite high FFA. Physiologic hyperinsulinemia during FFA elevation paradoxically decreased MBV (P < 0.05). This MBV decrease was reversed by either 0.1 Hz contraction or ET-1 receptor A antagonism, and the combination raised MBV above basal.

CONCLUSIONS

Contraction recruits microvasculature beyond that seen with physiologic hyperinsulinemia by a distinct mechanism that is not blocked by FFA-induced vascular insulin resistance. The paradoxical MBV decline seen with insulin plus FFA may result from differential inhibition of insulin-stimulated nitric oxide-dependent vasodilation relative to ET-1 vasoconstriction. Our results implicate ET-1 as a potential mediator of FFA-induced vascular insulin resistance.

A potential role for free fatty acids in the pathogenesis of preeclampsia

OBJECTIVE

Pregnant women with the vascular complication of preeclampsia show altered lipid metabolism characterized by elevated circulating triglycerides and nonesterified free fatty acids. We have compared the effect of maternal plasma from women with and without preeclampsia on cultured vascular endothelial cells and determined whether these plasma-induced changes were reproduced with free fatty acid solutions of palmitic, oleic and linoleic acid, representative of circulating levels reported in preeclampsia.

METHODS

Lipid accumulation was quantified by oil-red O staining, apoptosis by terminal dUTP nick-end labelling (TUNEL) and the measurement of mitochondrial redox capacity, and membrane potential recorded using MTT reduction and JC-1 accumulation for human umbilical vein endothelial cells (HUVECs) exposed to plasma and free fatty acids.

RESULTS

Lipid droplet accumulation was significantly increased in cultured HUVECs conditioned with maternal plasma from pregnancies with preeclampsia compared with normal uncomplicated controls. This increase was replicated following exposure to free fatty acids at the combined concentrations defined in preeclampsia. Plasma from these women also caused a significant decrease in mitochondrial dehydrogenase activity, a marked reduction in mitochondrial membrane potential and an increase in apoptosis compared with normal pregnancy. Again these effects were reproduced using free fatty acids in combination at the levels previously associated with preeclampsia.

CONCLUSION

These findings support the concept of a circulating pathogenic factor for preeclampsia and highlight the possibility that this factor is not a single compound but perhaps the combined elevation of the free fatty acids palmitic, oleic and linoleic acid in the maternal circulation.

Serum fatty acid binding protein 4, free fatty acids, and metabolic risk markers

Fatty acid binding protein (FABP) 4 chaperones free fatty acids (FFAs) in the adipocytes during lipolysis. Serum FFA relates to metabolic syndrome, and serum FABP4 is emerging as a novel risk marker. In 36 overweight/obese women, serum FABP4 and FFA were measured hourly during 5-hour oral glucose tolerance test. Insulin resistance was determined using frequently sampled intravenous glucose tolerance test. Serum lipids and inflammation markers were measured at fasting. During oral glucose tolerance test, serum FABP4 decreased by 40%, reaching its nadir at 3 hours (from 45.3 +/- 3.1 to 31.9 +/- 1.6 ng/mL), and stayed below the baseline at 5 hours (35.9 +/- 2.2 ng/mL) (P < .0001 for both, compared with the baseline). Serum FFA decreased by 10-fold, reaching a nadir at 2 hours (from 0.611 +/- 0.033 to 0.067 +/- 0.004 mmol/L), then rebounded to 0.816 +/- 0.035 mmol/L at 5 hours (P < .001 for both, compared with baseline). Both fasting FABP4 and nadir FABP4 correlated with obesity. Nadir FABP4 correlated also with insulin resistance parameters from frequently sampled intravenous glucose tolerance test and with inflammation. Nadir FFA, but not fasting FFA, correlated with the metabolic syndrome parameters. In conclusion, fasting FABP4 related to metabolic risk markers more strongly than fasting FFA. Nadir FABP4 and nadir FFA measured after glucose loading may provide better risk assessment than the fasting values.

Signaling mechanisms involved in altered function of macrophages from diet-induced obese mice affect immune responses

Recent research links diet-induced obesity (DIO) with impaired immunity, although the underlying mechanisms remain unclear. We find that the induction of inducible NO synthase (iNOS) and cytokines is suppressed in mice with DIO and in bone marrow macrophages (BMMPhi) from mice with DIO exposed to an oral pathogen, Porphyromonas gingivalis. BMMPhi from lean mice pre-treated with free fatty acids (FFAs) and exposed to P. gingivalis also exhibit a diminished induction of iNOS and cytokines. BMMPhi from lean and obese mice exposed to P. gingivalis and analyzed by a phosphorylation protein array show a reduction of Akt only in BMMPhi from mice with DIO. This reduction is responsible for diminished NF-kappaB activation and diminished induction of iNOS and cytokines. We next observed that Toll-like receptor 2 (TLR2) is suppressed in BMMPhi from DIO mice whereas carboxy-terminal modulator protein (CTMP), a known suppressor of Akt phosphorylation, is elevated. This elevation stems from defective TLR2 signaling. In BMMPhi from lean mice, both FFAs and TNF-alpha--via separate pathways--induce an increase in CMTP. However, in BMMPhi from DIO mice, TLR2 can no longer inhibit the TNF-alpha-induced increase in CTMP caused by P. gingivalis challenge. This defect can then be restored by transfecting WT TLR2 into BMMPhi from DIO mice. Thus, feeding mice a high-fat diet over time elevates the CTMP intracellular pool, initially via FFAs activating TLR2 and later when the defective TLR2 is unable to inhibit TNF-alpha-induced CTMP. These findings unveil a link between obesity and innate immunity.

Dietary fatty acids differentially regulate production of TNF-alpha and IL-10 by murine 3T3-L1 adipocytes

OBJECTIVE

Obesity correlates with increased production of adipocyte-derived cytokines, which may contribute to a chronic subclinical inflammation seen in obese individuals. This study evaluated the ability of specific fatty acids to modulate production of the proinflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), and the anti-inflammatory cytokine, interleukin-10 (IL-10), in murine 3T3-L1 adipocytes. Effects on nuclear factor-kappaB (NF-kappaB), a key transcriptional activator of the inflammatory cascade, and suppressor of cytokine signaling 3 (SOCS-3), a negative regulator of cytokine signaling, were also determined.

METHODS AND PROCEDURES

Adipocytes were incubated for 24 and 48 h with and without 50 or 500 micromol/l of palmitic acid, oleic acid, or docosahexaenoic acid, (DHA). Effects on gene expression and protein secretion of TNF-alpha and IL-10 were determined using real-time PCR and a murine multipex RIA kit. SOCS-3 expression was determined by northern blotting and NF-kappaB binding activity was assessed using a commercially available assay.

RESULTS

Adipocytes treated for 24 h with palmitic acid exhibited a 70% increase in TNF-alpha production and up to a 75% decrease in IL-10 production, relative to untreated cells. In contrast, DHA treatment had no effect on TNF-alpha, but increased IL-10 production twofold. No effect of oleic acid was seen on either TNF-alpha or IL-10 production. Similar results were obtained during a 48-h incubation. Furthermore, NF-kappaB DNA-binding activity increased fourfold in response to palmitic acid and decreased 60% in response to DHA. Expression of SOCS-3 increased twofold in DHA-treated cells.

DISCUSSION

In aggregate, these results suggest that dietary fatty acids act directly on adipocytes to modulate cytokine production. As circulating fatty acids levels are chronically elevated in obese individuals, this effect may account in part for obesity-associated inflammation.

Attenuation of vascular/neural dysfunction in Zucker rats treated with enalapril or rosuvastatin

OBJECTIVE

Obese Zucker rats, animal model for the metabolic syndrome, develop a diabetes-like neuropathy that is independent of hyperglycemia. The purpose of this study was to determine whether drugs used to treat cardiovascular dysfunction in metabolic syndrome also protect nerve function.

METHODS AND PROCEDURES

Obese Zucker rats at 20 weeks of age were treated for 12 weeks with enalapril or rosuvastatin. Lean rats were used as controls. Vasodilation in epineurial arterioles was measured by videomicroscopy. Endoneurial blood flow (EBF) was measured by hydrogen clearance and nerve conduction velocity was measured following electrical stimulation of motor or sensory nerves.

RESULTS

Enalapril treatment decreased serum angiotensin-converting enzyme (ACE) activity and both drugs reduced serum cholesterol levels. In obese Zucker rats at 32 weeks of age superoxide levels were elevated in the aortas and epineurial arterioles, which were reduced by treatment with either drug. Nitrotyrosine levels were increased in epineurial arterioles and reduced with enalapril treatment. EBF was decreased and corrected by treatment with either drug. Motor nerve conduction velocity was decreased and significantly improved with enalapril treatment. Obese Zucker rats were hypoalgesic in response to a thermal stimulus and this was significantly improved with either treatment. Treatment with either enalapril or rosuvastatin significantly reversed the decrease in acetylcholine-mediated vascular relaxation of epineurial arterioles in obese Zucker rats.

DISCUSSION

Even though obese Zucker rats have normal glycemia vascular and neural dysfunctions develop with age and can be improved by treatment with either enalapril or rosuvastatin.

Fasting nonesterified fatty acid profiles in childhood and their relationship with adiposity, insulin sensitivity, and lipid levels

OBJECTIVE

The objective of this study was to examine the major constituent of nonesterified fatty acids in children with respect to auxologic parameters, insulin sensitivity, and lipid levels, because nonesterified fatty acid levels are elevated in obesity and are important in the development of comorbidities.

METHODS

Fasting blood samples were obtained from 73 children (43 girls; 49 obese; median [range] age: 11.4 [0.9-17.6] years). Concentrations of the major circulating nonesterified fatty acids (myristate, palmitate, oleate, stearate, and arachidate) were determined by gas chromatography mass spectrometry, alongside measurement of insulin, adiponectin, and lipid profiles.

RESULTS

The sum of all nonesterified fatty acids was significantly higher in obese versus normal-weight children, although gender (but not age or puberty) was an important determinant, with the difference remaining significant only in boys. Overall, obese children had higher concentrations of myristate, palmitate, and oleate but not stearate or arachidate. Age was an important determinant of myristate and arachidate, whereas gender proved more important for palmitate and stearate. Fasting insulin concentrations were not associated with either total nonesterified fatty acid concentrations or any of the individual nonesterified fatty acids, although a positive correlation was found between adiponectin and total nonesterified fatty acid concentrations that was independent of obesity status and that seemed mediated by changes in palmitate and stearate. Serum total cholesterol and low-density lipoprotein (but not high-density lipoprotein) levels seemed to correlate positively with circulating concentrations of palmitate, oleate, and stearate, whereas serum triacylglycerols correlated with myristate, palmitate, and oleate concentrations.

CONCLUSIONS

Nonesterified fatty acid concentrations are elevated in obese children, primarily as a result of increases in myristate, palmitate, and oleate. Independent effects of nonesterified fatty acids on circulating adiponectin levels and lipid parameters were observed, although we found no relationship between nonesterified fatty acid concentrations and the insulin resistance identified with obesity.

The effects of estrogen and testosterone on gene expression in the rat mesenteric arteries

A dramatic difference exists in the timing of development of cardiovascular disease in men vs. women. The primary candidates underlying the cause of this gender difference are the sex steroids, estrogen and testosterone. The vasculature is considered to be a site of action of these steroids. In spite of these concepts there is little data on the direct effects of estrogen and testosterone on gene expression in the vasculature. In this study, ovariectomized Sprague Dawley rats were treated for 4 days with vehicle (sesame oil), estradiol benzoate (0.15 mg/kg/day), or testosterone (1 mg/kg/day). The mesenteric arteries were obtained, total RNA was extracted, and CodeLink Uniset Rat I DNA microarrays were used to identify differential gene expression. Seven genes were identified as differentially expressed from the DNA microarray data and confirmed by real time RT-PCR. The expression of D site albumin promoter binding protein and fatty acid synthase were increased in response to both estrogen and testosterone. 3 alpha-hydroxysteroid dehydrogenase, interleukin 4 receptor, JunB and c-Fos expression were increased by estrogen but not by testosterone. Aryl hydrocarbon nuclear translocator-like gene was reduced by testosterone. These data identify genes not previously known to be responsive to estrogen and testosterone in the vasculature.

Obesity and obesity-initiated metabolic syndrome: mechanistic links to chronic kidney disease

There is an epidemic of obesity and the metabolic syndrome in the United States and across the world. Both entities are associated with high mortality, mainly as a result of cardiovascular disease. The epidemic of obesity has been paralleled by an increase in the incidence of chronic kidney disease (CKD). Several recent epidemiologic studies have shown that obesity and the metabolic syndrome are independent predictors of CKD. In addition to diabetes and hypertension, several other mechanisms have been postulated to initiate and maintain kidney injury in patients with obesity and the metabolic syndrome. This article reviews the recent epidemiologic data linking obesity and the metabolic syndrome to CKD and summarizes the potential mechanisms of renal injury in this setting, with a focus on the role of inflammation, lipotoxicity, and hemodynamic factors. Potential preventive and therapeutic modalities based on the limited evidence available are discussed.

Fat Cell‐Derived Modulators of Vascular Cell Pathophysiology: The List Keeps Growing

Independent of the association of obesity with dyslipidemia, hypertension, and increased propensity for diabetes, fatness per se is increasingly recognized as a cardiovascular offender. That adipose tissue releases a wide range of adipokines, growth factors, enzymes, and enzyme substrates linked to vascular injury provides a plausible explanation for the role of fat in vascular disease: tumor necrosis factor-alpha, leptin, resistin, interleukin-1, -6, -8, and -18, serum amyloid A, monocyte chemoattractant protein I, macrophage inhibitory factor, aortic carboxypeptidase, hepa-rin-binding epidermal growth factor-like growth factor, vascular endothelial growth factor, transforming growth factor beta, angiotensinogen, cathepsin S, estradiol, cortisol, mineralocorticoid releasing factor, and calcitonin peptides are probable fat-derived prothrombotic, proinflammatory, and proatherosclerotic agents acting in a paracrine and/or endocrine manner. Other adipocyte products such as adiponectin, transforming growth factor beta, and interleukin-10 exert some antiatherogenic effects. The following is a short overview of how adipose tissue products affect the vasculature.

Palmitate and oleate have distinct effects on the inflammatory phenotype of human endothelial cells

Free fatty acids may create a state of continuous and progressive damaging to the vascular wall manifested by endothelial dysfunction. In this study we determine the mechanisms by which fatty acids palmitate (C16:0) and oleate (C18:1) affect intracellular long chain acyl-CoA (LCAC) content, energy metabolism, cell survival and proliferation and activation of NF-kappaB in cultured endothelial cells. A 48-h exposure of human umbilical vein endothelial cells (HUVEC) to 0.5 mM palmitate or 0.5 mM oleate increased total long chain acyl-CoA (LCAC) content 1.7 and 2 fold, respectively and decreased ATP(total)/ADP(total) ratio by 26+/-5% (mean+/-SEM) and 15+/-2%, respectively, which was prevented by the acyl-CoA synthetase inhibitor triacsin C. Furthermore, palmitate inhibited cell proliferation by 34+/-5%, while oleate stimulated it by 12+/-2%. alpha-Tocopherol fully and triacsin C partially abolished the effect of palmitate on cell proliferation. Palmitate and oleate increased caspase-3 activity 3.2 and 1.4 fold, respectively. Palmitate-induced caspase-3 activation was prevented by triacsin C and slightly reduced by alpha-tocopherol and by the de novo ceramide synthesis inhibitor fumonisin B(1). Both fatty acids induced antioxidant-sensitive nuclear translocation of NF-kappaB after 72 h, but not after 48 h. In conclusion, we showed that fatty acids influence different aspects of HUVEC function resulting in amongst other activation of apoptotic and inflammatory pathways. Our results indicate that the effects depend on the fatty acid type and may be related to accumulation of LCAC.

Acarbose improves fibrinolytic activity in patients with impaired glucose tolerance

Acarbose has been shown to ameliorate insulinemia, suggesting that it may exert favorable effects on the impaired fibrinolytic state in prediabetic patients. We therefore conducted a randomized controlled study to examine the effects of acarbose on fibrinolysis in patients with impaired glucose tolerance (IGT). The participants were randomized to receive (n = 20) or not (control, n = 20) 100 mg of acarbose before each meal (300 mg/d) for 3 months. A marked decrease in the plasma levels of plasminogen activator inhibitor 1 (by 42%) and fibrinogen (by 27%) was observed in the acarbose group at the end of the study, whereas no significant changes in the levels of these parameters were observed in the control group. We also conducted postprandial evaluation of insulin-related clinical markers and found ameliorated hyperinsulinemia in the subjects treated with acarbose. These results indicate that acarbose could improve fibrinolysis in patients with IGT, mainly by ameliorating insulinemia. Other favorable effects of acarbose, such as reduction in the plasma levels of oxidized low-density lipoprotein, glucose toxicity, and hyperglycemia, might also contribute, at least in part, to the beneficial effects of the drug on the fibrinolytic state in patients with IGT.

Fat as an endocrine organ: relationship to the metabolic syndrome

Obesity and the metabolic syndrome have both reached pandemic proportions. Together they have the potential to impact on the incidence and severity of cardiovascular pathologies, with grave implications for worldwide health care systems. The metabolic syndrome is characterized by visceral obesity, insulin resistance, hypertension, chronic inflammation, and thrombotic disorders contributing to endothelial dysfunction and, subsequently, to accelerated atherosclerosis. Obesity is a key component in development of the metabolic syndrome and it is becoming increasingly clear that a central factor in this is the production by adipose cells of bioactive substances that directly influence insulin sensitivity and vascular injury. In this paper, we review advances in the understanding of biologically active molecules collectively referred to as "adipokines" and how dysregulated production of these factors in obese states mediates the pathogenesis of obesity associated metabolic syndrome.

Thiazolidinediones

Our knowledge and understanding of the role played by peroxisome proliferator-activated gamma receptors in physiology and pathophysiology has expanded dramatically over the past 5 years. Originally described as having important functions in adipogenesis and glucose homeostasis, their pharmacologic agonists, the thiazolidinediones, were introduced as antihyperglycemic, insulin-sensitizing agents for the management of type 2 diabetes mellitus. However, it was to some degree inevitable that the thiazolidinediones would be rapidly recognized as having vasculoprotective properties beyond glycemic control that might also be beneficial. First, diabetic complications are vascular in nature, the earliest feature of these is endothelial dysfunction. Second, it is being increasingly appreciated that these complications develop through inflammatory and procoagulant pathways in which increased oxidative stress is considered a major etiologic mechanism, and which are closely linked to the presence of insulin resistance, visceral obesity, and hyperglycemia. Early appreciation that the thiazolidinediones have antioxidant, anti-inflammatory, anti-procoagulant, and antiproliferative properties in addition to their insulin-sensitizing, anti-lipotoxic properties created a marriage of investigative pathways that has not only led to a very large body of literature on the pleiotropic effects of thiazolidinediones, but also to the development of new understandings of the connections between insulin resistance, obesity, and hyperglycemia and the onset of vascular disease. Understandably, most of the focus has been directed at the macrovascular complications of diabetes, since these are the major causes of morbidity and mortality in this population. However, there is evidence that these agents may have benefits for the microvascular complications as well, and their potential role for cardiovascular disease prevention in non-diabetic patients with the metabolic syndrome is a logical extension of the work performed in diabetes. The recently reported results of the effects of pioglitazone versus placebo on cardiovascular events in patients with type 2 diabetes support the contention that these agents have vasculoprotective effects.