Adipose tissue regulates hepatic cholesterol metabolism via adiponectin

Insights into the pivotal role of statins and its nanoformulations in hyperlipidemia

Hyperlipidemia is the primary cause of heart disorders and has been manifested as the condition with remarkable higher levels of very-low-density lipoproteins, low-density lipoproteins, intermediate-density lipoprotein, triglycerides, and cholesterol in blood circulation. Genetic causes or systemic metabolic illnesses like diabetes mellitus, increased alcohol consumption, hypothyroidism, and primary biliary cirrhosis are several reasons behind development of hyperlipidemia. Higher levels of lipids and lipoproteins in plasma are responsible for various health disorders in human body like occlusion of blood vessels, acute pancreatitis, and reduced artery lumen elasticity. Both primary and secondary prophylaxis of heart disease can be achieved through combination of pharmacologic therapy with therapeutic lifestyle adjustments. Statins which belongs to HMG-CoA reductase inhibitors are preferred for primary prevention of hyperlipidemia particularly for individuals at higher risk of development of heart disease. This review discusses the recent advancements and outcomes of nanoparticle drug carriers for statins in the therapy of hyperlipidemia.

Polymorphisms of adiponectin gene and gene–lipid interaction with hypertension risk in Chinese coal miners: A matched case-control study

Objective

Low serum adiponectin level can predict hypertension development, and adiponectin gene (ADIPOQ) polymorphisms have been reported to be linked with hypertension risk. Whereas, the interaction between ADIPOQ polymorphisms and environmental factors on the susceptibility of hypertension remained unclear. The purpose of this study was to explore the relationship of ADIPOQ polymorphisms with hypertension risk and their interaction with lipid levels in coal miners.

Methods

A matched case-control study with 296 case-control pairs was performed in a large coal mining group located in North China. The participants were questioned by trained interviewers, and their ADIPOQ genotype and lipid levels were determined. Logistic regression, stratified analysis, and crossover analysis were applied to evaluate the effects of rs2241766, rs1501299, and rs266729 genotypes and gene–lipid interaction on hypertension risk.

Results

In this matched case-control study, the genotypes of rs2241766 TG+GG, rs1501299 GT+TT, and rs266729 CG+GG were marginally related to hypertension risk. Individuals with high total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) level were susceptible to hypertension (TC: odds ratio [OR] = 1.807, 95% confidence intervals [95%CI] = 1.266–2.581; LDL-C: OR = 1.981, 95%CI = 1.400–2.803; HDL-C: OR = 1.559, 95%CI = 1.093–2.223). Antagonistic interactions were detected between rs2241766 and TC, rs1501299 and TC, rs2241766 and LDL-C, and rs1501299 and HDL-C (rs2241766 and TC: OR = 0.393, 95%CI = 0.191–0.806; rs1501299 and TC: OR = 0.445, 95%CI = 0.216–0.918; rs2241766 and LDL-C: OR = 0.440, 95%CI = 0.221–0.877; rs1501299 and HDL-C: OR = 0.479, 95%CI = 0.237–0.967). Stratified analysis showed that hypertension risk was high for the subjects with rs2241766 TG+GG or rs1501299 GG under the low lipid level but low for those under the high lipid level. In the case group, the TC and LDL-C levels for rs2241766 TG+GG were lower than those for rs2241766 GG, and the TC and HDL-C levels for rs1501299 GT+TT were higher than those for rs1501299 GG.

Conclusions

Although the effects of ADIPOQ polymorphisms alone were not remarkable, an antagonistic interaction was observed between ADIPOQ polymorphisms and lipid levels.

The role of adiponectin in cholesterol efflux and HDL biogenesis and metabolism

Cholesterol efflux is the initial step in the reverse cholesterol transport pathway by which excess cholesterol in peripheral cells is exported and subsequently packaged into high-density lipoprotein (HDL) particles. Adiponectin is the most abundantly secreted adipokine that possesses anti-inflammatory and vasculoprotective properties via interaction with transmembrane receptors, AdipoR1 and AdipoR2. Evidence suggests that low levels of adiponectin may be a useful marker for atherosclerotic disease. A proposed anti-atherogenic mechanism of adiponectin involves its ability to promote cholesterol efflux. We performed a systematic review of the role of adiponectin in cholesterol efflux and HDL biogenesis, and of the proteins and receptors believed to be implicated in this process. Nineteen eligible studies (7 clinical, 11 fundamental, 1 clinical + fundamental) were identified through Ovid Medline, Ovid Embase, and Pubmed, that support the notion that adiponectin plays a key role in promoting ABCA1-dependent cholesterol efflux and in modulating HDL biogenesis via activation of the PPAR-γ/LXR-α signalling pathways in macrophages. AdipoR1 and AdipoR2 are suggested to also be implicated in this process, however the data are conflicting/insufficient to establish any firm conclusions. Once the exact mechanisms are unravelled, adiponectin may be critical in defining future treatment strategies directed towards increasing HDL functionality and ultimately reducing atherosclerotic disease.

Natural products for controlling hyperlipidemia: review

Hyperlipidemia is an abnormality of lipid metabolism, characterized by an elevation of total cholesterol, triglyceride, and low density lipoprotein-cholesterol, and/or a decreasing of high density lipoprotein cholesterol in circulating levels. Hyperlipidemia has been ranked as one of the greatest risk factors contributing to prevalence and severity of coronary heart diseases. Hyperlipidemia-associated lipid disorders are considered the cause of atherosclerotic cardiovascular disease. There has been a growing interest in natural products and their role in the maintenance and improvement of health and wellness. The cholesterol-lowering effect of dietary plants has been well studied and various natural products were shown to be helpful in lowering plasma cholesterol levels and encouraging safety profile. The main focus of this review is to describe what we know to date of natural products, along with their lipid-lowering mechanisms, which are either through inhibition of cholesterol absorption, inhibition of cholesterol synthesis or antioxidant mechanisms.

Elevated 4β-hydroxycholesterol/cholesterol ratio in anorexia nervosa patients

Recent studies have shown that the cytochrome P450 (CYP) 3A phenotype marker 4β-hydroxycholesterol/cholesterol (4βOHC/C) ratio is negatively correlated with body weight in healthy volunteers, and that obese patients have lower 4βOHC levels than healthy controls. However, 4βOHC/C ratio in underweight patients has yet to be reported. The aim of this study was to examine potential differences in CYP3A activity between underweight patients with anorexia nervosa and normal-weight volunteers by measuring plasma 4βOHC/C ratio. Furthermore, we wished to describe any association between body mass index (BMI) and 4βOHC/C ratio in underweight patients. A total of 20 underweight patients and 16 normal-weight volunteers were included in the study, all females. Underweight patients had a median 4βOHC/C ratio (molar ratio × 10-5) of 2.52 (range, 0.90-11.3) compared to 1.29 (0.56-2.09) in normal-weight subjects (Mann-Whitney P = 0.0005). 4βOHC/C ratio was negatively correlated with BMI in underweight patients (r = -0.56, P = 0.011), and in the whole study population (r = -0.67, P < 0.0001). This suggests that the negative correlation between 4βOHC/C and BMI, which has previously been reported between 4βOHC/C and body weight in healthy volunteers, extends to underweight patients. The findings indicate that CYP3A activity increases with decreasing BMI, resulting in higher CYP3A activity in underweight patients compared to normal-weight subjects. The potential clinical relevance of this needs to be studied further by comparing pharmacokinetics of drugs subjected to CYP3A-mediated metabolism in underweight vs. normal-weight individuals.

Leptin and adiponectin levels in major depressive disorder: A systematic review and meta-analysis

OBJECTIVES

To explore differences in adipokine levels (i.e., leptin and adiponectin levels) between adults with Major Depressive Disorder (MDD) and healthy controls (HC), and to discuss the possible role of adipokine regulation in the development and progression of MDD.

METHODS

A systematic review and meta-analysis were conducted based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. A systematic search was conducted for all English and Chinese peer-reviewed articles from inception to November 2017. A random effects model was used to calculate the standardized mean difference (SMD) of leptin and/or adiponectin levels in subjects diagnosed with MDD versus HC within a 95% confidence interval (CI).

RESULTS

Thirty-three studies were included in this meta-analysis. In total, 4,372 (52.3%) subjects with MDD and 3,984 (47.7%) HC were compared. We identified significant lower adiponectin levels in MDD compared to HC with a small effect size (ES) (SMD = -0.25; 95% CI: -0.48, -0.02; P < 0.001). However, no significant difference was observed in leptin levels between MDD subjects and HC (SMD = 0.13; 95% CI: -0.06, 0.31; P = 0.170). The heterogeneity in the results of our meta-analysis could not be completely explained by dividing subjects into subgroups. Results from subgroup analyses suggested that studies involving samples with BMI ≥ 25 had lower adiponectin levels in subjects with MDD compared to HC, and older age samples (i.e., age ≥ 40) with BMI ≥ 25 had both higher leptin levels and lower adiponectin levels in MDD subjects as compared to HC.

LIMITATIONS

The heterogeneity of included studies, small sample sizes, and potential publication bias were significant limitations.

CONCLUSIONS

The current systematic review and meta-analysis indicated that lower adiponectin levels may be associated with MDD. Moreover, the results suggest that males expressing lower adiponectin and leptin levels have an increased likelihood of developing MDD. Future studies should aim to investigate the manifestation of depressive phenotypes in older, obese populations with altered metabolic profiles resulting from adipokine dysregulation. The review has been registered with PROSPERO (registration number CRD42018082733).

Tumor necrosis factor- α, adiponectin and their ratio in gestational diabetes mellitus

Background:

It has been suggested that inflammation might be implicated in the gestational diabetes mellitus (GDM) complications, including insulin resistance. The aims of the current study were to explore maternal circulating values of TNF-α, adiponectin and the adiponectin/TNF-α ratio in women with GDM compared with normal pregnancy and their relationships with metabolic syndrome biomarkers.

Methods:

Forty women with GDM and 40 normal pregnant women were included in the study. Commercially available enzyme-linked immunosorbent assay methods were used to measure serum levels of TNF-α and total adiponectin.

Results:

Women with GDM had higher values of TNF-α (225.08±27.35 vs 115.68±12.64 pg/ml, p<0.001) and lower values of adiponectin (4.50±0.38 vs 6.37±0.59 µg/ml, p=0.003) and the adiponectin/TNF-α ratio (4.31±0.05 vs 4.80±0.07, P<0.001) than normal pregnant women. The adiponectin/TNF-α ratio showed negative correlations with insulin resistance (r=-0.68, p<0.001) and triglyceride (r=-0.39, p=0.014) and a positive correlation with insulin sensitivity (r=0.69, p<0.001). Multiple linear regression analysis showed that values of the adiponectin /TNF-α ratio were independently associated with insulin resistance. Binary logistic regression analysis showed that GDM was negatively associated with adiponectin /TNF-α ratio.

Conclusions:

In summary, the adiponectin/TNF-α ratio decreased significantly in GDM compared with normal pregnancy. The ratio might be an informative biomarker for assessment of pregnant women at high risk of insulin resistance and dyslipidemia and for diagnosis and therapeutic monitoring aims in GDM.

Combination of berberine and evodiamine inhibits intestinal cholesterol absorption in high fat diet induced hyperlipidemic rats

BACKGROUND

Hyperlipidemia characterized of elevated serum lipid levels is a prevalent disease frequently resulting in cardiovascular disease (CVD). Berberine and evodiamine are herbal products of traditional Chinese herb Coptis chinensis and Evodia rutaecarpa, which are indicated to exert regulation of lipid metabolism. Therefore, the objective of this study was to investigate the lipid-lowering effect of berberine and evodiamine combination in hyperlipidemic rats.

METHOD

The rat model of hyperlipidemia was established by providing high-fat-diet (HFD) for 4 weeks. Berberine (BB), evodiamine (EV), and their combination (BB + EV) were orally administered to HFD induced rats for 4 weeks. Body weight, food utilization, histopathology of liver tissues, lipid profiles of serum and liver were measured. Gas chromatography (GC) analysis was applied to examine the level of plasma total cholesterol and ß- Sitosterol (BS) to estimate cholesterol absorption activity. Furthermore, intestinal NPC1L1, ACAT2, and ApoB48 protein expressions were evaluated by immunohistochemical assay.

RESULT

According to the results, decreased levels of serum cholesterol (TC), triglycerides (TG), low density lipoprotein-cholesterol (LDL-C), as well as hepatic TC were showed in hyperlipidemic rats treated by combination of berberine and evodiamine. GC analysis indicated that the elevated plasma BS was significantly ameliorated by BB, EV, and BB + EV. In addition, immunohistochemical analysis revealed that BB + EV treatment down-regulated the expressions of intestinal NPC1L1 and ACAT2, and ApoB48 in HFD induced rats.

CONCLUSION

Based on the above results, combination of berberine and evodiamine exerted a promising preventive effect on hyperlipidemia, partially through inhibiting intestinal absorption of cholesterol.

High maysin corn silk extract reduces body weight and fat deposition in C57BL/6J mice fed high-fat diets

BACKGROUNG/OBJECTIVES

The study was performed to investigate the effects and mechanisms of action of high maysin corn silk extract on body weight and fat deposition in experimental animals.

MATERIALS/METHODS

A total of 30 male C57BL/6J mice, 4-weeks-old, were purchased and divided into three groups by weight using a randomized block design. The normal-fat (NF) group received 7% fat (diet weight basis), the high-fat (HF) group received 25% fat and 0.5% cholesterol, and the high-fat corn silk (HFCS) group received high-fat diet and high maysin corn silk extract at 100 mg/kg body weight through daily oral administration. Body weight and body fat were measured, and mRNA expression levels of proteins involved in adipocyte differentiation, fat accumulation, fat synthesis, lipolysis, and fat oxidation in adipose tissue and the liver were measured.

RESULTS

After experimental diet intake for 8 weeks, body weight was significantly lower in the HFCS group compared to the HF group (P < 0.05), and kidney fat and epididymal fat pad weights were significantly lower in the HFCS group compared to the HF group (P < 0.05). In the HFCS group, CCAAT/enhancer binding protein-β, peroxisome proliferator-activated receptor-γ1 (PPAR-γ1), and PPAR-γ2 mRNA expression levels were significantly reduced (P < 0.05) in the epididymal fat pad, whereas cluster of differentiation 36, lipoprotein lipase, acetyl-CoA carboxylase-1, sterol regulatory element binding protein-1c, pyruvate dehydrogenase kinase, isozyme-4, glucose-6-phosphate dehydrogenase, and stearoyl-CoA desaturase-1 mRNA expression levels were significantly decreased in liver and adipose tissues (P < 0.05). In the HFCS group, mRNA expression levels of AMP-activated protein kinase, hormone-sensitive lipase, and carnitine palmitoyltransferase-1 were elevated (P < 0.05).

CONCLUSIONS

It can be concluded that high maysin corn silk extract inhibits expression of genes involved in adipocyte differentiation, fat accumulation, and fat synthesis as well as promotes expression of genes involved in lipolysis and fat oxidation, further inhibiting body fat accumulation and body weight elevation in experimental animals.

The Mechanisms Underlying the Hypolipidaemic Effects of Grifola frondosa in the Liver of Rats

The present study investigated the hypolipidaemic effects of Grifola frondosa and its regulation mechanism involved in lipid metabolism in liver of rats fed a high-cholesterol diet. The body weights and serum lipid levels of control rats, of hyperlipidaemic rats, and of hyperlipidaemic rats treated with oral G. frondosa were determined. mRNA expression and concentration of key lipid metabolism enzymes were investigated. Serum cholesterol, triacylglycerol, and low-density lipoprotein cholesterol levels were markedly decreased in hyperlipidaemic rats treated with G. frondosa compared with untreated hyperlipidaemic rats. mRNA expression of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), acyl-coenzyme A: cholesterol acyltransferase (ACAT2), apolipoprotein B (ApoB), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC1) were significantly down-regulated, while expression of cholesterol 7-alpha-hydroxylase (CYP7A1) was significantly up-regulated in the livers of treated rats compared with untreated hyperlipidaemic rats. The concentrations of these enzymes also paralleled the observed changes in mRNA expression. Two-dimensional polyacrylamide gel electrophoresis (2-DE) and Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS) were used to identify 20 proteins differentially expressed in livers of rats treated with G. frondosa compared with untreated hyperlipidemic rats. Of these 20 proteins, seven proteins were down-regulated, and 13 proteins were up-regulated. These findings indicate that the hypolipidaemic effects of G. frondosa reflected its modulation of key enzymes involved in cholesterol and triacylglycerol biosynthesis, absorption, and catabolic pathways. G. frondosa may exert anti-atherosclerotic effects by inhibiting LDL oxidation through down-regulation and up-regulating proteins expression in the liver of rats. Therefore, G. frondosa may produce both hypolipidaemic and anti-atherosclerotic effects, and potentially be of use as a functional food for the treatment or prevention of hyperlipidaemia and atherosclerosis.

Corn silk extract improves cholesterol metabolism in C57BL/6J mouse fed high-fat diets

BACKGROUND/OBJECTIVES

Corn silk (CS) extract contains large amounts of maysin, which is a major flavonoid in CS. However, studies regarding the effect of CS extract on cholesterol metabolism is limited. Therefore, the purpose of this study was to determine the effect of CS extract on cholesterol metabolism in C57BL/6J mouse fed high-fat diets.

MATERIALS/METHODS

Normal-fat group fed 7% fat diet, high-fat (HF) group fed 25% fat diet, and high-fat with corn silk (HFCS) group were orally administered CS extract (100 mg/kg body weight) daily. Serum and hepatic levels of total lipids, triglycerides, and total cholesterol as well as serum free fatty acid, glucose, and insulin levels were determined. The mRNA expression levels of acyl-CoA: cholesterol acyltransferase (ACAT), cholesterol 7-alpha hydroxylase (CYP7A1), farnesoid X receptor (FXR), lecithin cholesterol acyltransferase (LCAT), low-density lipoprotein receptor, 3-hyroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase), adiponectin, leptin, and tumor necrosis factor α were determined.

RESULTS

Oral administration of CS extract with HF improved serum glucose and insulin levels as well as attenuated HF-induced fatty liver. CS extracts significantly elevated mRNA expression levels of adipocytokines and reduced mRNA expression levels of HMG-CoA reductase, ACAT, and FXR. The mRNA expression levels of CYP7A1 and LCAT between the HF group and HFCS group were not statistically different.

CONCLUSIONS

CS extract supplementation with a high-fat diet improves levels of adipocytokine secretion and glucose homeostasis. CS extract is also effective in decreasing the regulatory pool of hepatic cholesterol, in line with decreased blood and hepatic levels of cholesterol though modulation of mRNA expression levels of HMG-CoA reductase, ACAT, and FXR.

Dietary Niacin Supplementation Suppressed Hepatic Lipid Accumulation in Rabbits

An experiment was conducted to investigate the effect of niacin supplementation on hepatic lipid metabolism in rabbits. Rex Rabbits (90 d, n = 32) were allocated to two equal treatment groups: Fed basal diet (control) or fed basal diet with additional 200 mg/kg niacin supplementation (niacin). The results show that niacin significantly increased the levels of plasma adiponectin, hepatic apoprotein B and hepatic leptin receptors mRNA (p<0.05), but significantly decreased the hepatic fatty acid synthase activity and adiponectin receptor 2, insulin receptor and acetyl-CoA carboxylase mRNA levels (p<0.05). Plasma insulin had a decreasing tendency in the niacin treatment group compared with control (p = 0.067). Plasma very low density lipoproteins, leptin levels and the hepatic adiponectin receptor 1 and carnitine palmitoyl transferase 1 genes expression were not significantly altered with niacin addition to the diet (p>0.05). However, niacin treatment significantly inhibited the hepatocytes lipid accumulation compared with the control group (p<0.05). In conclusion, niacin treatment can decrease hepatic fatty acids synthesis, but does not alter fatty acids oxidation and triacylglycerol export. And this whole process attenuates lipid accumulation in liver. Besides, the hormones of insulin, leptin and adiponectin are associated with the regulation of niacin in hepatic lipid metabolism in rabbits.

Adipokines, metabolic dysfunction and illness course in bipolar disorder

Replicated evidence indicates that individuals with BD are differentially affected by metabolic comorbidities and that its occurrence is a critical mediator and/or moderator of BD outcomes. This study aimed to explore the role of adipokines on bipolar disorder (BD) course and its relationship with metabolic comorbidities (i.e. type 2 diabetes mellitus, obesity). We measured plasma levels of adiponectin and leptin, as well as anthropometric and metabolic parameters of 59 patients with BD and 28 healthy volunteers. Our results showed that, in female participants, adiponectin was lower in individuals with BD, relative to healthy controls (p = 0.017). In the BD population, adiponectin levels were correlated with fasting glucose (r = -0.291, p = 0.047), fasting insulin (r = -0.332, p = 0.023), C-peptide (r = 0.040, p = 0.040), homeostatic model assessment-insulin resistance (r = -0.411, p = 0.004), HDL (r = 0.508, p < 0.001), VLDL (r = -0.395, p = 0.005) and triglycerides (r = -0.310, p = 0.030). After adjustment for age, gender and BMI, individuals with BD and low adiponectin levels (i.e. < 7.5 μg/ml), had a higher number of mood episodes (p < 0.001), lower number of psychiatric hospitalizations (p = 0.007), higher depressive symptoms (p < 0.001) and lower levels of functioning (p = 0.020). In conclusion, adiponectin levels, either directly or as a proxy of metabolic dysfunction, is independently associated with an unfavorable course of illness in BD.

Dietary fat and carbohydrate modulate the effect of the ATP-binding cassette A1 (ABCA1) R230C variant on metabolic risk parameters in premenopausal women from the Genetics of Atherosclerotic Disease (GEA) Study

Background

Although the R230C-ATP-binding cassette A1 (ABCA1) variant has been consistently associated with HDL-C levels, its association with diabetes and other metabolic parameters is unclear. Estrogen and dietary factors are known to regulate ABCA1 expression in different tissues. Thus, we aimed to explore whether gender, menopausal status and macronutrient proportions of diet modulate the effect of this variant on various metabolic parameters.

Methods

One thousand five hundred ninety-eight controls from the GEA study were included (787 men, 363 premenopausal women and 448 menopausal women), previously assessed for anthropometric and biochemical measurements and visceral to subcutaneous abdominal fat (VAT/SAT) ratio on computed tomography. Taqman assays were performed for genotyping. Diet macronutrient proportions were assessed using a food frequency questionnaire validated for the Mexican population. Multivariate regression models were constructed to assess the interaction between the proportion of dietary macronutrients and the R230C polymorphism on metabolic parameters.

Results

All significant interactions were observed in premenopausal women. Those carrying the risk allele and consuming higher carbohydrate/lower fat diets showed an unfavorable metabolic pattern [lower HDL-C and adiponectin levels, higher VAT/SAT ratio, homeostasis model assessment for insulin resistance (HOMA-IR) and higher gamma-glutamyl transpeptidase (GGT) and alkaline phosphatase (ALP) levels]. Conversely, premenopausal women carrying the risk allele and consuming lower carbohydrate/higher fat diets showed a more favorable metabolic pattern (higher HDL-C and adiponectin levels, and lower VAT/SAT ratio, HOMA-IR, GGT and ALP levels).

Conclusion

This is the first study reporting a gender-specific interaction between ABCA1/R230C variant and dietary carbohydrate and fat percentages affecting VAT/SAT ratio, GGT, ALP, adiponectin levels and HOMA index. Our study confirmed the previously reported gender-specific ABCA1-diet interaction affecting HDL-C levels observed in an independent study. Our results show how gene-environment interactions may help further understand how certain gene variants confer metabolic risk, and may provide information useful to design diet intervention studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-015-0040-3) contains supplementary material, which is available to authorized users.