Determinación y caracterización de esteroles no colesterol en tejido adiposo

En el mundo occidental, la obesidad, conocida como un peso corporal desproporcionado con respecto a la estatura, se ha convertido en la epidemia del siglo XXI. Como consecuencia del aumento calórico excesivo, se producen una serie de cambios metabólicos en los diferentes territorios adiposos, que podrían actuar como biomarcadores de sobrepeso u obesidad. El objetivo principal de este estudio fue optimizar un método analítico para determinar colesterol y oxiesteroles en tejido adiposo por HPLC-MS/MS para estudiar posteriormente estos biomarcadores en mujeres con sobrepeso y obesidad. Se determinó colesterol y oxiesteroles en tejido adiposo control y tejido adiposo subcutáneo y visceral de 38 mujeres mayores de edad con índices de masa corporal (IMC) comprendidos entre 23 y 40,1 kg/m2. Se obtuvieron unas concentraciones de colesterol y oxiesteroles en tejido adiposo subcutáneo mayores en mujeres con IMC≤31 kg/m2 que en mujeres con IMC>31 kg/m2. Sin embargo, en tejido adiposo visceral las mujeres con IMC>31 kg/m2 tuvieron concentraciones mayores de colesterol y oxiesteroles. En tejido adiposo subcutáneo se encontró una relación inversa entre el colesterol y el IMC, al contrario que en tejido adiposo visceral donde la relación fue directa. Hubo una relación directa entre el colesterol y los oxiesteroles tanto en tejido adiposo subcutáneo como en visceral, siendo estadísticamente significativa con el 27-hidroxicolesterol y con el 24S-hidroxicolesterol, respectivamente. En conclusión, el tejido adiposo subcutáneo y el visceral parecen comportarse de manera diferente a la hora de acumular colesterol y oxiesteroles en función del IMC en las mujeres estudiadas. Los resultados obtenidos tienen una significación estadística muy baja en algunos casos, por lo que sería de interés continuar este trabajo con un mayor tamaño muestral. Futuros estudios de los oxiesteroles en suero y en tejido adiposo, podrían ofrecer un análisis más global del metabolismo del colesterol en la obesidad.<br /

Bile acid synthesis precursors in subjects with genetic hypercholesterolemia negative for LDLR/APOB/PCSK9/APOE mutations. Association with lipids and carotid atherosclerosis

Some oxysterols are precursors of bile acid synthesis and play an important role in cholesterol homeostasis. However, if they are involved in the pathogeny of genetic hypercholesterolemia has not been previously explored. We have studied non-cholesterol sterol markers of cholesterol synthesis (lanosterol and desmosterol) and oxysterols (7a-hydroxy-4-cholesten-3-one, 24S-hydroxycholesterol and 27-hydroxycholesterol) in 200 affected subjects with primary hypercholesterolemia of genetic origin, negative for mutations in LDLR, APOB, PCSK9 and APOE genes (non-FH GH) and 100 normolipemic controls. All studied oxysterols and cholesterol synthesis markers were significantly higher in affected subjects than controls (P < 0.001). Ratios of oxysterols to total cholesterol were higher in non-FH GH than in controls, although only 24S-hydroxycholesterol showed statistical significance (P < 0.001). Cholesterol synthesis markers had a positive correlation with BMI, triglycerides, cholesterol and apoB in control population. However, these correlations disappeared in non-FH GH with the exception of a weak positive correlation for non-HDL cholesterol and apoB. The same pattern was observed for oxysterols with high positive correlation in controls and absence of correlation for non-FH GH, except non-HDL cholesterol for 24S-hydroxycholesterol and 27-hydroxycholesterol and apoB for 27-hydroxycholesterol. All non-cholesterol sterols had positive correlation among them in patients and in controls. A total of 65 (32.5%) and 35 (17.5%) affected subjects presented values of oxysterols ratios to total cholesterol above the 95th percentile of the normal distribution (24S-hydroxycholesterol and 27-hydroxycholesterol, respectively). Those patients with the highest levels of 24S-hydroxycholesterol associated an increase in the carotid intima media thickness. These results suggest that bile acid metabolism is affected in some patients with primary hypercholesterolemia of genetic origin, negative for mutations in the candidate genes, and may confer a higher cardiovascular risk. Our results confirm that cholesterol synthesis overproduction is a primary defect in non-HF GH and suggest that subjects with non-FH GH show high levels of oxysterols in response to hepatic overproduction of cholesterol

Different protein composition of low-calorie diet differently impacts adipokine profile irrespective of weight loss in overweight and obese women

Background and aims: High-protein (HP) diets have shown benefits in cardiometabolic markers such as insulin or triglycerides but the responsible mechanisms are not known. We aimed to assess the effect of three energy-restricted diets with different protein contents (20%, 27%, and 35%; similar to 80% coming from animal source) on plasma adipokine concentration and its association with changes in cardiometabolic markers. Methods: Seventy-six women (BMI 32.8 +/- 2.93) were randomized to one of three calorie-reduced diets, with protein, 20%, 27%, or 35%; carbohydrates, 50%, 43%, or 35%; and fat, 30%, for 3 months. Plasma adipokine (leptin, resistin, adiponectin, and retinol-binding protein 4; RBP4) levels were assessed. Results: After 3 months, leptin concentration decreased in all groups without differences among them, while resistin levels remained unchanged. Adiponectin concentration heterogeneously changed in all groups (P for trend = 0.165) and resistin concentration did not significantly change. RPB4 significantly decreased by -17.5% (-31.7, -3.22) in 35%-protein diet (P for trend = 0.024 among diets). Triglycerides improved in women following the 35%-protein diet regardless of weight loss; RBP4 variation significantly influenced triglyceride concentration change by 24.9% and 25.9% when comparing 27%- and 35%- with 20%-protein diet, respectively. Conclusions: A 35%-protein diet induced a decrease in RBP4 regardless of weight loss, which was directly associated with triglyceride concentration improvement. These findings suggest that HP diets improve the cardiometabolic profile, at least in part, through changes in adipokine secretion. Whether this beneficial effect of HP diet is due to improvements in hepatic or adipose tissue functionality should be elucidated

Frequency of rare mutations and common genetic variations in severe hypertriglyceridemia in the general population of Spain

Background: Hypertriglyceridemia (HTG) is a common complex metabolic trait that results of the accumulation of relatively common genetic variants in combination with other modifier genes and environmental factors resulting in increased plasma triglyceride (TG) levels. The majority of severe primary hypertriglyceridemias is diagnosed in adulthood and their molecular bases have not been fully defined yet. The prevalence of HTG is highly variable among populations, possibly caused by differences in environmental factors and genetic background. However, the prevalence of very high TG and the frequency of rare mutations causing HTG in a whole non-selected population have not been previously studied. Methods: The total of 23, 310 subjects over 18 years from a primary care-district in a middle-class area of Zaragoza (Spain) with TG >500 mg/dL were selected to establish HTG prevalence. Those affected of primary HTG were considered for further genetic analisys. The promoters, coding regions and exon-intron boundaries of LPL, LMF1, APOC2, APOA5, APOE and GPIHBP1 genes were sequenced. The frequency of rare variants identified was studied in 90 controls. Results: One hundred ninety-four subjects (1.04 %) had HTG and 90 subjects (46.4 %) met the inclusion criteria for primary HTG. In this subgroup, nine patients (12.3 %) were carriers of 7 rare variants in LPL, LMF1, APOA5, GPIHBP1 or APOE genes. Three of these mutations are described for the first time in this work. The presence of a rare pathogenic mutation did not confer a differential phenotype or a higher family history of HTG. Conclusion: The prevalence of rare mutations in candidate genes in subjects with primary HTG is low. The low frequency of rare mutations, the absence of a more severe phenotype or the dominant transmission of the HTG would not suggest the use of genetic analysis in the clinical practice in this population

Association of cholesterol and oxysterols in adipose tissue with obesity and metabolic syndrome traits

Adipose tissue stores a substantial amount of body cholesterol in humans. Obesity is associated with decreased concentrations of serum cholesterol. During weight gain, adipose tissue dysfunction might be one of the causes of metabolic syndrome. The aim of this study is to evaluate cholesterol storage and oxidized metabolites in adipose tissue and their relationship with metabolic clinical characteristics

Effect of bergamot on lipid profile in humans: A systematic review

Dyslipidemia is a well-established modifiable cardiovascular risk. Although statins can reduce LDLc by 50-60%, less than 20% of patients with high risk of CVD achieve LDL targets. The aim of this systematic review is to evaluate the effect of the nutraceutical, bergamot (Citrus bergamia), on lipid parameters in humans. PubMed, Embase, Cochrane Library, and Google Scholar databases were searched for interventional and observational studies investigating the effect of bergamot on lipid profile in humans. This systematic review retrieved a total of 442 studies of which 12 articles fulfilled the eligibility criteria and were included in the qualitative synthesis. Based on data, 75% of studies showed a significant decrease in total cholesterol, triglycerides and LDLc. The decrease in total cholesterol varied from 12.3% to 31.3%, from 7.6% to 40.8% in LDLc and from 11.5% to 39.5% in triglycerides. Eight trials reported HDLc increase after intervention with bergamot. Overall, a dose-dependent and possible synergistic effect when administering with statins can be deducted from these trials. It is essential to point out that studies had heterogeneous designs and scientific quality of studies was quite limited. Promising findings reveal an alternative therapeutic option in dyslipidemia management with bergamot supplementation, especially in subjects with statins intolerance

Genetic predictors of weight loss in overweight and obese subjects

The aim of our study was to investigate a large cohort of overweight subjects consuming a homogeneous diet to identify the genetic factors associated with weight loss that could be used as predictive markers in weight loss interventions. We retrospectively recruited subjects (N = 788) aged over 18 years with a Body Mass Index (BMI) between 25 and 40 kg/m(2) who were treated at our lipid unit for at least one year from 2008 to 2016, and we also recruited a control group (168 patients) with normal BMIs. All participants received counselling from a nutritionist that included healthy diet and physical activity recommendations. We genotyped 25 single nucleotide variants (SNVs) in 25 genes that were previously associated with obesity and calculated genetic scores that were derived from 25 SNVs. The risk allele in CADM2 showed a higher frequency in overweight and obese subjects than in controls (p = 0.007). The mean follow-up duration was 5.58 +/- 2.68 years. Subjects with lower genetic scores showed greater weight loss during the follow-up period. The genetic score was the variable that best explained the variations in weight from the baseline. The genetic score explained 2.4% of weight change variance at one year and 1.6% of weight change variance at the end of the follow-up period after adjusting for baseline weight, sex, age and years of follow-up

ABCG5/G8 gene is associated with hypercholesterolemias without mutation in candidate genes and non-cholesterol sterols

Context Approximately 20% to 40% of clinically defined familial hypercholesterolemia (FH) cases do not show a causative mutation in candidate genes (mutation-negative FH), and some of them may have a polygenic origin. Objective The aim of this work was to study the prevalence of ABCG5/G8 genetic variants in mutation-negative FH, as defects in these genes relate to intestinal hyperabsorption of cholesterol and thus ABCG5/G8 variants could explain in part the mechanism of hypercholesterolemia. Design, setting, and patients We sequenced the ABCG5/G8 genes in 214 mutation-negative FH and 97 controls. Surrogate markers of cholesterol absorption (5?-cholestanol, ?-sitosterol, campesterol, stigmasterol, and sitostanol) were quantified by high-performance liquid chromatography?tandem mass spectrometry in both studied groups. Results We found 8 mutation-negative FH patients (3.73%) with a pathogenic mutation in ABCG5/G8 genes. We observed significantly higher concentration of surrogate markers of cholesterol absorption in mutation-negative FH than in controls. In addition, we found significantly higher concentrations of cholesterol absorption markers in mutation-negative FH with ABCG5/G8 defects than in mutation-negative, ABCG5/G8-negative FH. A gene score reflecting the number of common single nucleotide variants associated with hypercholesterolemia was significantly higher in cases than in controls (P = .032). Subjects with a gene score above the mean had significantly higher 5?-cholestanol and stigmasterol than those with a lower gene score. Conclusions Mutation-negative FH subjects accumulate an excess of rare and common gene variations in ABCG5/G8 genes. This variation is associated with increased intestinal absorption of cholesterol, as determined by surrogate makers, suggesting that these loci contribute to hypercholesterolemia by enhancing intestinal cholesterol absorption.This study was supported by grants from the Spanish Ministry of Economy and Competitiveness PI15/01983, PI13/02507, PI12/01321, CIBERCV, CIBEROBN, and Cuenca Villoro Foundation. These projects are co-financed by Instituto de Salud Carlos III and the European Regional Development Fund (ERDF) of the European Union “A way to make Europe.

Simvastatin reduces circulating oxysterol levels in men with hypercholesterolemia

Oxysterols (OHC) are biologically active cholesterol metabolites circulating in plasma that may be formed enzymatically (e.g. 24S-OHC, 25S-OHC and 27-OHC) or by autoxidative mechanisms (e.g. 7-ketocholesterol, 7β-OHC and 25S-OHC). Oxysterols are more soluble than cholesterol and are reported to exert inflammatory, cytoprotective and apoptotic effects according to concentration and species. Esterified oxysterols have been analysed in people with dementia and cardiovascular diseases although there is no consistent relationship between oxysterol esters and disease. However, oxysterol esters are held in lipoprotein core and may not relate to the concentration and activity of plasma free oxysterols. Methodological limitations have challenged the analysis of free oxysterols to date. We have developed a fast, sensitive and specific quantitative LC-MS/MS, multiple reaction monitoring (MRM) method to target five oxysterols in human plasma with analyte recoveries between 72-82 % and sensitivities between 5-135ng. A novel method was used to investigate the hypothesis that simvastatin may reduce the concentrations of specific plasma free oxysterols in hypercholesterolaemia. Twenty healthy male volunteers were recruited (aged 41-63 years); ten were asymptomatic with high plasma cholesterol >6.5mM and ten were healthy with normal plasma cholesterol (<6.5mM). Simvastatin (40mg/day) was prescribed to those with hypercholesterolaemia. Plasma samples were taken from both groups at baseline and after three months. Simvastatin reduced plasma cholesterol by ~35% (p<0.05) at the end of three months. Oxysterols generated by autoxidation but not enzymatically were elevated more than 100 fold in hypercholesterolaemic midlife men. Plasma oxysterols were restored to those of healthy controls after simvastatin intervention suggesting that autoxidation is either prevented by simvastatin directly or that autoxidation is less prevalent when plasma cholesterol concentrations are in the normal range