Prevention and reversal of lipotoxicity-induced hepatic insulin resistance and steatohepatitis in mice by an antioxidant carotenoid, β-cryptoxanthin

Association between dietary vitamin A intake from different sources and non-alcoholic fatty liver disease among adults

Non-alcoholic fatty liver disease (NAFLD) has become an urgent public health issue with high global prevalence, but data on NAFLD are inconsistent. The association of total dietary vitamin A intake with the NAFLD risk was not well documented in previous studies. To explore the relationship between dietary vitamin A intake from different sources and NAFLD risk among American adults. Data were collected from the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2014. Logistic regression and restricted cubic spline models were used to estimate the relationship between total dietary vitamin A intake and NAFLD risk. 6,613 adult participants were included. After adjusting potential confounders, the odds ratios (ORs) with 95% confidence intervals (CIs) of NAFLD for the highest quartile intake of total vitamin A, preformed vitamin A, provitamin A carotenoids were respectively 0.86 (0.69-1.06), 0.97 (0.74-1.28), and 0.78 (0.61-0.99), compared to the lowest quartile. Stratifying gender and age, provitamin A carotenoids intake was inversely associated with NAFLD risk in females and participants aged < 45 years. Dose-response analysis indicated a linear negative relationship between provitamin A carotenoids intake and NAFLD risk. Provitamin A carotenoids intake was inversely associated with NAFLD, especially in women and those aged < 45 years among adult American.

Effects of oral β-cryptoxanthin administration on the transcriptomes of peripheral neutrophil and liver tissue using microarray analysis in post-weaned Holstein calves

We investigated the effects of oral administration of β-cryptoxanthin (β-CRX), a precursor of vitamin A synthesis, on the transcriptomes of peripheral neutrophils and liver tissue in post-weaned Holstein calves with immature immunity. A single oral administration of β-CRX (0.2 mg/kg body weight) was performed in eight Holstein calves (4.0 ± 0.8 months of age; 117 ± 10 kg) on Day 0. Peripheral neutrophils (n = 4) and liver tissue (n = 4) were collected on Days 0 and 7. Neutrophils were isolated by density gradient centrifugation and treated with the TRIzol reagent. mRNA expression profiles were examined by microarray and differentially expressed genes were investigated using the Ingenuity Pathway Analysis software. The differentially expressed candidate genes identified in neutrophils (COL3A1, DCN, and CCL2) and liver tissue (ACTA1) were involved in enhanced bacterial killing and maintenance of cellular homoeostasis respectively. The changes in the expression of six of the eight common genes encoding enzymes (ADH5 and SQLE) and transcription regulators (RARRES1, COBLL1, RTKN, and HES1) were in the same direction in neutrophils and liver tissue. ADH5 and SQLE are involved in the maintenance of cellular homoeostasis by increasing the availability of substrates, and RARRES1, COBLL1, RTKN, and HES1 are associated with the suppression of apoptosis and carcinogenesis. An in silico analysis revealed that MYC, which is related to the regulation of cellular differentiation and apoptosis, was the most significant upstream regulator in neutrophils and liver tissue. Transcription regulators such as CDKN2A (cell growth suppressor) and SP1 (cell apoptosis enhancer) were significantly inhibited and activated, respectively, in neutrophils and liver tissue. These results suggest that oral administration of β-CRX promotes the expression of candidate genes related to bactericidal ability and regulation of cellular processes in peripheral neutrophils and liver cells in response to the immune-enhancing function of β-CRX in post-weaned Holstein calves.

Traditional Chinese medicines and natural products targeting immune cells in the treatment of metabolic-related fatty liver disease

MAFLD stands for metabolic-related fatty liver disease, which is a prevalent liver disease affecting one-third of adults worldwide, and is strongly associated with obesity, hyperlipidemia, and type 2 diabetes. It encompasses a broad spectrum of conditions ranging from simple liver fat accumulation to advanced stages like chronic inflammation, tissue damage, fibrosis, cirrhosis, and even hepatocellular carcinoma. With limited approved drugs for MAFLD, identifying promising drug targets and developing effective treatment strategies is essential. The liver plays a critical role in regulating human immunity, and enriching innate and adaptive immune cells in the liver can significantly improve the pathological state of MAFLD. In the modern era of drug discovery, there is increasing evidence that traditional Chinese medicine prescriptions, natural products and herb components can effectively treat MAFLD. Our study aims to review the current evidence supporting the potential benefits of such treatments, specifically targeting immune cells that are responsible for the pathogenesis of MAFLD. By providing new insights into the development of traditional drugs for the treatment of MAFLD, our findings may pave the way for more effective and targeted therapeutic approaches.

Anti-Obesity and Anti-Inflammatory Synergistic Effects of Green Tea Catechins and Citrus β-Cryptoxanthin Ingestion in Obese Mice

Chronic obesity causes various diseases, leading to an urgent need for its treatment and prevention. Using monosodium-glutamate-induced obesity mice, the present study investigated the synergistic obesity-reducing effects of tea catechins and the antioxidant β-cryptoxanthin present in mandarin oranges. The results show that the obese mice that ingested both tea catechin and β-cryptoxanthin for 4 weeks had a significantly decreased body weight, with no difference in body weight compared with control mice. Moreover, the blood biochemical test results were normal, and the body fat percentage was significantly decreased according to the histopathological analysis. Additionally, the abundance of M1 macrophages, which release pro-inflammatories, was significantly reduced in adipose tissue. Indeed, a significant decrease was detected in M1-macrophage-secreted tumor necrosis factor-alpha levels. Meanwhile, M2 macrophage levels were recovered, and adiponectin, which is released from adipocytes and involved in suppressing metabolic syndrome, was increased. Collectively, these results suggest that the combination of tea catechins and antioxidant foods can alleviate chronic obesity, indicating that a combination of various ingredients in foods might contribute to reducing chronic obesity.

A Glimpse into Milestones of Insulin Resistance and an Updated Review of Its Management

Insulin is the main metabolic regulator of fuel molecules in the diet, such as carbohydrates, lipids, and proteins. It does so by facilitating glucose influx from the circulation into the liver, adipose tissue, and skeletal myocytes. The outcome of which is subjected to glycogenesis in skeletal muscle and lipogenesis in adipose tissue, as well as in the liver. Therefore, insulin has an anabolic action while, on the contrary, hypoinsulinemia promotes the reverse process. Protein breakdown in myocytes is also encountered during the late stages of diabetes mellitus. The balance of the blood glucose level in physiological conditions is maintained by virtue of the interactive functions of insulin and glucagon. In insulin resistance (IR), the balance is disturbed because glucose transporters (GLUTs) of cell membranes fail to respond to this peptide hormone, meaning that glucose molecules cannot be internalized into the cells, the consequence of which is hyperglycemia. To develop the full state of diabetes mellitus, IR should be associated with the impairment of insulin release from beta-cells of the pancreas. Periodic screening of individuals of high risk, such as those with obesity, hypercholesterolemia, and pregnant nulliparous women in antenatal control, is vital, as these are important checkpoints to detect cases of insulin resistance. This is pivotal as IR can be reversed, provided it is detected in its early stages, through healthy dietary habits, regular exercise, and the use of hypoglycemic agents. In this review, we discuss the pathophysiology, etiology, diagnosis, preventive methods, and management of IR in brief.

Lutein ameliorates high-fat diet-induced obesity, fatty liver, and glucose intolerance in C57BL/6J mice

Obesity is a multi-factorial metabolic syndrome that increases the risk of cardiovascular diseases, diabetes, and cancer. We recently demonstrated the antiadipogenic efficacy of lutein using a 3 T3-L1 cell culture model. This study aimed to examine the antiobesity efficacy of lutein on high-fat (60% kcal fat) diet-induced C57BL/6J obese mice model. Lutein (300 and 500 μM), Orlistat (30 mg/kg body weight - positive control), and its combination (orlistat, 15 mg/kg body weight+lutein, 300 μM) were administered in high-fat diet (HFD)-fed mice every other day for 24 weeks. The effect on serum and hepatic lipid parameters was estimated using biochemical assay kits. The adipose tissue expression of adipocyte differentiation markers at gene and protein levels was analyzed by RT-PCR and western blotting, respectively. The results showed that lutein administration and drug significantly reduced epididymal and abdominal adipose tissue weights. Further, lutein reduced the serum cholesterol and LDL-C concentration compared to the HFD group. The HFD-induced elevation in the hepatic triglycerides and cholesterol levels were significantly blocked by lutein and its combination with the drug. Similarly, lutein and its drug combination efficiently lowered the HFD-mediated elevated blood glucose levels. Lutein downregulated the expression of CEBP-α, PPAR-γ, and FAS in the epididymal adipose tissue. Thus, supplementation of lutein may control diet-induced obesity and associated complications in the human population.

Terpenoids: Natural Compounds for Non-Alcoholic Fatty Liver Disease (NAFLD) Therapy

Natural products have been the most productive source for the development of drugs. Terpenoids are a class of natural active products with a wide range of pharmacological activities and therapeutic effects, which can be used to treat a variety of diseases. Non-alcoholic fatty liver disease (NAFLD), a common metabolic disorder worldwide, results in a health burden and economic problems. A literature search was conducted to obtain information relevant to the treatment of NAFLD with terpenoids using electronic databases, namely PubMed, Web of Science, Science Direct, and Springer, for the period 2011-2021. In total, we found 43 terpenoids used in the treatment of NAFLD. Over a dozen terpenoid compounds of natural origin were classified into five categories according to their structure: monoterpenoids, sesquiterpenoids, diterpenoids, triterpenoids, and tetraterpenoids. We found that terpenoids play a therapeutic role in NAFLD, mainly by regulating lipid metabolism disorder, insulin resistance, oxidative stress, and inflammation. The AMPK, PPARs, Nrf-2, and SIRT 1 pathways are the main targets for terpenoid treatment. Terpenoids are promising drugs and will potentially create more opportunities for the treatment of NAFLD. However, current studies are restricted to animal and cell experiments, with a lack of clinical research and systematic structure-activity relationship (SAR) studies. In the future, we should further enrich the research on the mechanism of terpenoids, and carry out SAR studies and clinical research, which will increase the likelihood of breakthrough insights in the field.

Suppression of obesity by melatonin through increasing energy expenditure and accelerating lipolysis in mice fed a high-fat diet

Backgrounds/objectives

Melatonin promotes brown adipose tissue (BAT) activity, leading to body mass reduction and energy expenditure. However, the mechanisms governing these beneficial effects are not well-established. This study aimed to assess the effects of (1) melatonin on BAT and energy metabolism, and (2) fibroblast growth factor 21 (FGF21) in BAT-mediated thermogenesis.

Methods

Male C57BL/6 J mice received a high-fat diet (HFD) or normal chow, accompanied by intraperitoneal injection of 20 mg/kg melatonin for 12 weeks. FGF21^−/− mice consumed an HFD with or without melatonin for 8 weeks.

Results

Melatonin attenuated weight gain, insulin resistance, adipocyte hypertrophy, inflammation, and hepatic steatosis induced by the HFD and increased energy expenditure. Furthermore, melatonin improved cold tolerance by increasing BAT uncoupling protein 1 (UCP1) expression and producing heat. Notably, melatonin resulted in a shift in energy metabolism favouring the utilization of fat, and it increased FGF21 in circulating and metabolic tissues and skeletal muscle phosphorylation of AMP-activated protein kinase. However, melatonin did not protect against obesity, insulin resistance, and energy expenditure in HFD-fed FGF21^−/− mice.

Conclusions

Melatonin suppressed obesity and insulin resistance resulting from the HFD by enhancing BAT activity and energy expenditure, and these effects were dependent on FGF21.

Targeted therapeutics and novel signaling pathways in non-alcohol-associated fatty liver/steatohepatitis (NAFL/NASH)

Non-alcohol-associated fatty liver/steatohepatitis (NAFL/NASH) has become the leading cause of liver disease worldwide. NASH, an advanced form of NAFL, can be progressive and more susceptible to developing cirrhosis and hepatocellular carcinoma. Currently, lifestyle interventions are the most essential and effective strategies for preventing and controlling NAFL without the development of fibrosis. While there are still limited appropriate drugs specifically to treat NAFL/NASH, growing progress is being seen in elucidating the pathogenesis and identifying therapeutic targets. In this review, we discussed recent developments in etiology and prospective therapeutic targets, as well as pharmacological candidates in pre/clinical trials and patents, with a focus on diabetes, hepatic lipid metabolism, inflammation, and fibrosis. Importantly, growing evidence elucidates that the disruption of the gut-liver axis and microbe-derived metabolites drive the pathogenesis of NAFL/NASH. Extracellular vesicles (EVs) act as a signaling mediator, resulting in lipid accumulation, macrophage and hepatic stellate cell activation, further promoting inflammation and liver fibrosis progression during the development of NAFL/NASH. Targeting gut microbiota or EVs may serve as new strategies for the treatment of NAFL/NASH. Finally, other mechanisms, such as cell therapy and genetic approaches, also have enormous therapeutic potential. Incorporating drugs with different mechanisms and personalized medicine may improve the efficacy to better benefit patients with NAFL/NASH.

β-cryptoxanthin alleviates myocardial ischaemia/reperfusion injury by inhibiting NF-κB-mediated inflammatory signalling in rats

The present study aimed to explore the function and molecular mechanism of β-cryptoxanthin on myocardial ischaemia-reperfusion injury (MIRI). Left anterior descending coronary artery ligation with reperfusion was utilised to establish a MIRI rat model. The results indicated that β-cryptoxanthin decreases infarct size and ameliorates signs of pathological histology in MIRI. TNF-α, IL-1β, and IL-6 levels in the serum were attenuated in response to β-cryptoxanthin treatment, serum LDH and CK-MB activities were also decreased. Immunohistochemical analysis and western blot results suggested that p65 was translocated to the nucleus in the I/R injury rat model. However, in the β-cryptoxanthin administration group, p65 expression and activity in the nucleus were decreased in a dose-dependent manner. Furthermore, p-p38 MAPK levels in response to β-cryptoxanthin were decreased, indicating that MAPK is involved in NF-κB signalling pathway regulation. In conclusion, β-cryptoxanthin alleviates myocardial ischaemia/reperfusion injury by inhibiting NF-κB-mediated inflammatory signalling in rats.

An Update on the Chemokine System in the Development of NAFLD

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the world. Sustained hepatic inflammation is a key driver of the transition from simple fatty liver to nonalcoholic steatohepatitis (NASH), the more aggressive form of NAFLD. Hepatic inflammation is orchestrated by chemokines, a family of chemoattractant cytokines that are produced by hepatocytes, Kupffer cells (liver resident macrophages), hepatic stellate cells, endothelial cells, and vascular smooth muscle cells. Over the last three decades, accumulating evidence from both clinical and experimental investigations demonstrated that chemokines and their receptors are increased in the livers of NAFLD patients and that CC chemokine ligand (CCL) 2 and CCL5 in particular play a pivotal role in inducing insulin resistance, steatosis, inflammation, and fibrosis in liver disease. Cenicriviroc (CVC), a dual antagonist of these chemokines’ receptors, CCR2 and CCR5, has been tested in clinical trials in patients with NASH-associated liver fibrosis. Additionally, recent studies revealed that other chemokines, such as CCL3, CCL25, CX3C chemokine ligand 1 (CX3CL1), CXC chemokine ligand 1 (CXCL1), and CXCL16, can also contribute to the pathogenesis of NAFLD. Here, we review recent updates on the roles of chemokines in the development of NAFLD and their blockade as a potential therapeutic approach.

Nutraceutic Potential of Bioactive Compounds of Eugenia dysenterica DC in Metabolic Alterations

The fruit and leaves of Eugenia dysenterica DC., locally known as cagaita, are rich in antioxidant glycosylated quercetin derivatives and phenolic compounds that have beneficial effects on diabetes mellitus, hypertension and general inflammation. We conducted a literature search to investigate the nutraceutical potentials of these phenolic compounds for treating obesity, diabetes mellitus and intestinal inflammatory disease. The phenolic compounds in E. dysenterica have demonstrated effects on carbohydrate metabolism, which can prevent the development of these chronic diseases and reduce LDL (low-density lipoprotein) cholesterol and hypertension. E. dysenterica also improves intestinal motility and microbiota and protects gastric mucosa, thereby preventing inflammation. However, studies are necessary to identify the mechanism by which E. dysenterica nutraceutical compounds act on such pathological processes to support future research.

A nutritional intervention that promotes increased vegetable intake in Japanese with non-alcoholic fatty liver disease: a six-month trial

The aim of this study was to investigate whether a nutritional intervention motivating increased vegetable consumption would be an effective treatment and diet therapy for patients with non-alcoholic fatty liver disease. We examined 15 patients with this disease (5 men and 10 women). During the 6-month intervention period, all participants received a small amount of vegetables twice a month as a nutritional education tool aimed at increasing vegetable consumption. They also received nutritional counseling and underwent ultrasound and blood biochemical examinations at baseline and 3 and 6 months after initiation of the intervention. Moreover, they were requested to submit dietary records for any 2 days. Green, white, and total vegetable intakes were significantly higher at 3 and 6 months than at baseline in 8 patients. These patients had significantly lower alanine amino­transferase and triglyceride concentrations than those whose vegetable intake did not increase. Additionally, green vegetable intake significantly negatively correlated with weight at 3 and 6 months (r = −0.617, p = 0.032 and r = −0.848, p = 0.008, respectively). These results suggest that our nutritional approach effectively increased vegetable consumption in at least some patients with non-alcoholic fatty liver disease, consequently improving their condition.

Macrophage Polarization and Its Role in Liver Disease

Macrophages are important immune cells in innate immunity, and have remarkable heterogeneity and polarization. Under pathological conditions, in addition to the resident macrophages, other macrophages are also recruited to the diseased tissues, and polarize to various phenotypes (mainly M1 and M2) under the stimulation of various factors in the microenvironment, thus playing different roles and functions. Liver diseases are hepatic pathological changes caused by a variety of pathogenic factors (viruses, alcohol, drugs, etc.), including acute liver injury, viral hepatitis, alcoholic liver disease, metabolic-associated fatty liver disease, liver fibrosis, and hepatocellular carcinoma. Recent studies have shown that macrophage polarization plays an important role in the initiation and development of liver diseases. However, because both macrophage polarization and the pathogenesis of liver diseases are complex, the role and mechanism of macrophage polarization in liver diseases need to be further clarified. Therefore, the origin of hepatic macrophages, and the phenotypes and mechanisms of macrophage polarization are reviewed first in this paper. It is found that macrophage polarization involves several molecular mechanisms, mainly including TLR4/NF-κB, JAK/STATs, TGF-β/Smads, PPARγ, Notch, and miRNA signaling pathways. In addition, this paper also expounds the role and mechanism of macrophage polarization in various liver diseases, which aims to provide references for further research of macrophage polarization in liver diseases, contributing to the therapeutic strategy of ameliorating liver diseases by modulating macrophage polarization.

Preventive Effects of β-Cryptoxanthin, a Potent Antioxidant and Provitamin A Carotenoid, on Lifestyle-Related Diseases-A Central Focus on Its Effects on Non-Alcoholic Fatty Liver Disease (NAFLD)

Humans usually get dietary carotenoids from foods such as green and yellow vegetables and algae. Carotenoids have been reported to effectively reduce the risk of developing lifestyle-related diseases. β-Cryptoxanthin, which is an antioxidative carotenoid and a type of provitamin A, is metabolically converted to vitamin A. β-Cryptoxanthin has recently gained attention for its risk-reducing effects on lifestyle-related diseases, especially on non-alcoholic fatty liver disease (NAFLD), from epidemiological, interventional, and mechanistic studies. Retinoids (vitamin A) have also been reported to be useful as a therapeutic agent for NAFLD. Provitamin A is known to serve as a supply source of retinoids through metabolic conversion by the regulated activity of β-carotene 15,15′-monooxygenase 1 (BCMO1) to the retina only when retinoids are deficient. From mechanistic studies using NAFLD-model mice, β-cryptoxanthin has been shown to contribute to the improvement of NAFLD through a multifaceted approach, including improved insulin resistance, suppression of oxidative stress and inflammation, a reduction of macrophages and a shift of their subsets, and control of lipid metabolism by peroxisome proliferator-activated receptor (PPAR) family activation, which are also expected to have clinical applications. β-Cryptoxanthin has the potential to prevent lifestyle-related diseases from different angles, not only as an antioxidant but also as a retinoid precursor.

CC chemokine ligand 3 deficiency ameliorates diet-induced steatohepatitis by regulating liver macrophage recruitment and M1/M2 status in mice

BACKGROUND AND AIMS

The global prevalence of nonalcoholic fatty liver disease (NAFLD) is increasing. Chemokines and their receptors have potential as therapeutic targets of NAFLD. We investigated the role of CC chemokine ligand 3 (CCL3) in the development of murine and human NAFLD.

METHODS

CCL3-knockout mice (CCL3^-/-) and littermate CCL3 wild-type control mice (WT) were fed a high-cholesterol and high-fat (CL) diet for 16 weeks to induce NAFLD. We investigated the impact of CCL3 gene deletion in bone marrow cells and leptin-deficient ob/ob mice on CL diet-induced steatohepatitis. We assayed the serum CCL3 levels in 36 patients with biopsy-proven NAFLD and nine healthy control subjects.

RESULTS

Compared with normal chow (NC), the CL diet induced steatohepatitis and hepatic fibrosis and elevated the plasma CCL3 level. In the liver, CCL3 protein colocalized with F4/80⁺ macrophages, especially CD11c⁺ M1-like macrophages, rather than other cell types. CCL3^-/- attenuated CL diet-induced steatohepatitis and fibrosis associated with M2-dominant liver macrophages compared with the WT. The reconstitution of bone marrow (BM) cells from CCL3^-/- attenuated steatohepatitis in WT mice fed a CL diet. Furthermore, crossing CCL3^-/- onto the ob/ob background prevented CL diet-induced NAFLD in ob/ob mice, which was associated with a lesser inflammatory phenotype of liver macrophages. Also, the serum and hepatic levels of CCL3 were significantly increased in patients with non-alcoholic steatohepatitis (NASH) compared to those with simple fatty liver (NAFL) and healthy subjects.

CONCLUSION

Our data indicate that CCL3 facilitates macrophage infiltration into the liver and M1 polarization in the progression of steatohepatitis and highlight the need for further studies to determine the effect of CCL3-CCR1 and -CCR5 signaling blockade on the treatment of NAFLD.

Antioxidant and Starch-Hydrolyzing Enzymes Inhibitory Properties of Striga-Resistant Yellow-Orange Maize Hybrids

Most of the health benefits derived from cereals are attributed to their bioactive compounds. This study evaluated the levels of the bioactive compounds, and the antioxidant and starch-hydrolyzing enzymes inhibitory properties of six pipeline Striga-resistant yellow-orange maize hybrids (coded AS1828-1, 4, 6, 8, 9, 11) in vitro. The maize hybrids were grown at the International Institute of Tropical Agriculture (IITA), Nigeria. The bioactive compounds (total phenolics, tannins, flavonoids, and phytate) levels, antioxidant (DPPH^• and ABTS^•+ scavenging capacity and reducing power) and starch-hydrolyzing enzymes (α-amylase and α-glucosidase) inhibitory activities of the maize hybrids were determined by spectrophotometry. At the same time, carotenoids were quantified using a reverse-phase HPLC system. The ranges of the bioactive compounds were: 11.25-14.14 mg GAE/g (total phenolics), 3.62-4.67 mg QE/g (total flavonoids), 3.63-6.29 mg/g (tannins), 3.66-4.31% (phytate), 8.92-12.11 µg/g (total xanthophylls), 2.42-2.89 µg/g (total β-carotene), and 3.17-3.77 µg/g (total provitamin A carotenoids). Extracts of the maize hybrids scavenged DPPH^• (SC₅₀: 9.07-26.35 mg/mL) and ABTS^•+ (2.65-7.68 TEAC mmol/g), reduced Fe³⁺ to Fe²⁺ (0.25 ± 0.64-0.43 ± 0.01 mg GAE/g), and inhibited α-amylase and α-glucosidase, with IC₅₀ ranges of 26.28-52.55 mg/mL and 47.72-63.98 mg/mL, respectively. Among the six clones of the maize hybrids, AS1828-9 had the highest (p < 0.05) levels of tannins and phytate and the strongest antioxidant and starch-hydrolyzing enzymes inhibitory activities. Significant correlations were observed between total phenolics and the following: ABTS^•+ (p < 0.01, r = 0.757), DPPH^• SC₅₀ (p < 0.01, r = -0.867), reducing power (p < 0.05, r = 0.633), α-amylase IC₅₀ (p < 0.01, r = -0.836) and α-glucosidase IC₅₀ (p < 0.05, r = -0.582). Hence, the Striga-resistant yellow-orange maize hybrids (especially AS1828-9) may be beneficial for alleviating oxidative stress and postprandial hyperglycemia.

Carotenoids: Therapeutic Strategy in the Battle against Viral Emerging Diseases, COVID-19: An Overview

Carotenoids, a group of phytochemicals, are naturally found in the Plant kingdom, particularly in fruits, vegetables, and algae. There are more than 600 types of carotenoids, some of which are thought to prevent disease, mainly through their antioxidant properties. Carotenoids exhibit several biological and pharmaceutical benefits, such as anti-inflammatory, anti-cancer, and immunity booster properties, particularly as some carotenoids can be converted into vitamin A in the body. However, humans cannot synthesize carotenoids and need to obtain them from their diets or via supplementation. The emerging zoonotic virus severe acute respiratory syndrome coronavirus 2, which causes coronavirus disease 2019 (COVID-19), originated in bats, and was transmitted to humans. COVID-19 continues to cause devastating international health problems worldwide. Therefore, natural preventive therapeutic strategies from bioactive compounds, such as carotenoids, should be appraised for strengthening physiological functions against emerging viruses. This review summarizes the most important carotenoids for human health and enhancing immunity, and their potential role in COVID-19 and its related symptoms. In conclusion, promising roles of carotenoids as treatments against emerging disease and related symptoms are highlighted, most of which have been heavily premeditated in studies conducted on several viral infections, including COVID-19. Further in vitro and in vivo research is required before carotenoids can be considered as potent drugs against such emerging diseases.

Anti-Inflammatory and Anticancer Effects of Microalgal Carotenoids

Acute inflammation is a key component of the immune system’s response to pathogens, toxic agents, or tissue injury, involving the stimulation of defense mechanisms aimed to removing pathogenic factors and restoring tissue homeostasis. However, uncontrolled acute inflammatory response may lead to chronic inflammation, which is involved in the development of many diseases, including cancer. Nowadays, the need to find new potential therapeutic compounds has raised the worldwide scientific interest to study the marine environment. Specifically, microalgae are considered rich sources of bioactive molecules, such as carotenoids, which are natural isoprenoid pigments with important beneficial effects for health due to their biological activities. Carotenoids are essential nutrients for mammals, but they are unable to synthesize them; instead, a dietary intake of these compounds is required. Carotenoids are classified as carotenes (hydrocarbon carotenoids), such as α- and β-carotene, and xanthophylls (oxygenate derivatives) including zeaxanthin, astaxanthin, fucoxanthin, lutein, α- and β-cryptoxanthin, and canthaxanthin. This review summarizes the present up-to-date knowledge of the anti-inflammatory and anticancer activities of microalgal carotenoids both in vitro and in vivo, as well as the latest status of human studies for their potential use in prevention and treatment of inflammatory diseases and cancer.

CX3CL1-CX3CR1 Signaling Deficiency Exacerbates Obesity-induced Inflammation and Insulin Resistance in Male Mice

The CX3CL1-CX3CR1 system plays an important role in disease progression by regulating inflammation both positively and negatively. We reported previously that C-C chemokine receptors 2 and 5 promote obesity-associated adipose tissue inflammation and insulin resistance. Here, we demonstrate that CX3CL1-CX3CR1 signaling is involved in adipose tissue inflammation and insulin resistance in obese mice via adipose tissue macrophage recruitment and M1/M2 polarization. Cx3cl1 expression was persistently decreased in the epididymal white adipose tissue (eWAT) of high-fat diet-induced obese (DIO) mice, despite increased expression of other chemokines. Interestingly, in Cx3cr1-/- mice, glucose tolerance, insulin resistance, and hepatic steatosis induced by DIO or leptin deficiency were exacerbated. CX3CL1-CX3CR1 signaling deficiency resulted in reduced M2-polarized macrophage migration and an M1-dominant shift of macrophages within eWAT. Furthermore, transplantation of Cx3cr1-/- bone marrow was sufficient to impair glucose tolerance, insulin sensitivity, and regulation of M1/M2 status. Moreover, Cx3cl1 administration in vivo led to the attenuation of glucose intolerance and insulin resistance. Thus, therapy targeting the CX3CL1-CX3CR1 system may be beneficial in the treatment of type 2 diabetes by regulating M1/M2 macrophages.

Lipidomics-Based Comparison of Molecular Compositions of Green, Yellow, and Red Bell Peppers

Identifying and annotating the molecular composition of individual foods will improve scientific understanding of how foods impact human health and how much variation exists in the molecular composition of foods of the same species. The complexity of this task includes distinct varieties and variations in natural occurring pigments of foods. Lipidomics, a sub-field of metabolomics, has emerged as an effective tool to help decipher the molecular composition of foods. For this proof-of-principle research, we determined the lipidomic profiles of green, yellow and red bell peppers (Capsicum annuum) using liquid chromatography mass spectrometry and a novel tool for automated annotation of compounds following database searches. Among 23 samples analyzed from 6 peppers (2 green, 1 yellow, and 3 red), over 8000 lipid compounds were detected with 315 compounds (106 annotated) found in all three colors. Assessments of relationships between these compounds and pepper color, using linear mixed effects regression and false discovery rate (<0.05) statistical adjustment, revealed 11 compounds differing by color. The compound most strongly associated with color was the carotenoid, β-cryptoxanthin (p-value = 7.4 × 10⁻⁵; FDR adjusted p-value = 0.0080). These results support lipidomics as a viable analytical technique to identify molecular compounds that can be used for unique characterization of foods.

Current innovations in nutraceuticals and functional foods for intervention of non-alcoholic fatty liver disease

As innovations in global agricultural production and food trading systems lead to major dietary shifts, high morbidity rates from non-alcoholic fatty liver disease (NAFLD), accompanied by elevated risk of lipid metabolism-related complications, has emerged as a growing problem worldwide. Treatment and prevention of NAFLD and chronic liver disease depends on the availability of safe, effective, and diverse therapeutic agents, the development of which is urgently needed. Supported by a growing body of evidence, considerable attention is now focused on interventional approaches that combines nutraceuticals and functional foods. In this review, we summarize the pathological progression of NAFLD and discuss the beneficial effects of nutraceuticals and the active ingredients in functional foods. We also describe the underlying mechanisms of these compounds in the intervention of NAFLD, including their effects on regulation of lipid homeostasis, activation of signaling pathways, and their role in gut microbial community dynamics and the gut-liver axis. In order to identify novel targets for treatment of lipid metabolism-related diseases, this work broadly explores the molecular mechanism linking nutraceuticals and functional foods, host physiology, and gut microbiota. Additionally, the limitations in existing knowledge and promising research areas for development of active interventions and treatments against NAFLD are discussed.

Haematococcus pluvialis Carotenoids Enrich Fractions Ameliorate Liver Fibrosis Induced by Thioacetamide in Rats: Modulation of Metalloproteinase and Its Inhibitor

Hepatic fibrosis is a consequence of chronic liver diseases. Metalloproteinase and its inhibitor have crucial roles in the resolution of liver fibrosis. The current relevant study is aimed to evaluate the therapeutic effect of Haematococcus pluvialis (H. pluvialis) extract, astaxanthin-rich fraction, astaxanthin ester-rich fraction, and β-carotene-rich fraction as well as their mechanisms of action in curing hepatic fibrosis induced by thioacetamide (TAA). Liver fibrosis was induced using TAA (intraperitoneal injection, two times a week for 6 weeks), in a rat model and H. pluvialis extract (200 mg/kg), and other fractions (30 mg/kg) were orally administered daily for 4 weeks after the last TAA injection. Based on HPLC analysis, H. pluvialis extract contains β-carotene (12.95 mg/g, extract) and free astaxanthin (10.85 mg/g, extract), while HPLC/ESI-MS analysis revealed that H. pluvialis extract contains 28 carotenoid compounds including three isomers of free astaxanthin, α or β-carotene, lutein, 14 astaxanthin mono-esters, 5 astaxanthin di-esters, and other carotenoids. H. pluvialis and its fractions reduced liver enzymes, nitric oxide, collagen 1, alpha-smooth muscle actin, and transforming growth factor-beta as well as elevated catalase antioxidant activity compared to the TAA group. Also, H. pluvialis extract and its fractions exceedingly controlled the balance between metalloproteinase and its inhibitor, activated Kupffer cells proliferation, and suppressed liver apoptosis, necrobiosis, and fibrosis. These findings conclude that H. pluvialis extract and its fractions have an antifibrotic effect against TAA-induced liver fibrosis by regulating the oxidative stress and proinflammatory mediators, suppressing multiple profibrogenic factors, and modulating the metalloproteinase and its inhibitor pathway, recommending H. pluvialis extract and its fractions for the development of new effective medicine for treating hepatic fibrosis disorders.

Prevention of NAFLD/NASH by Astaxanthin and β-Cryptoxanthin

Metabolic disorders, such as lipid accumulation, insulin resistance, and inflammation, have been implicated in the pathogenesis of NAFLD/NASH. Both innate and recruited immune cells mediate the development of insulin resistance and NASH. Oxidative stress is also pivotal for the progression of NASH. Astaxanthin is a natural carotenoid mainly derived from microorganisms and marine organisms. Due to its special chemical structure, astaxanthin has strong antioxidant activity. β-Cryptoxanthin is a xanthophyll carotenoid specifically found in the Satsuma mandarin. β-Cryptoxanthin is readily absorbed and relatively abundant in human plasma, together with α-carotene, β-carotene, lycopene, lutein, and zeaxanthin. Considering the unique chemical properties of astaxanthin and β-cryptoxanthin and the complex pathogenic mechanism of NASH, astaxanthin and β-cryptoxanthin are regarded as a considerable compound for the prevention and treatment of NASH. This chapter comprehensively describes the mechanism of the application for astaxanthin and β-cryptoxanthin on the prevention and treatment of NASH from the aspects, including antioxidative stress, inhibition of inflammation and promotion of M2 macrophage polarization, improvement of mitochondrial oxidative respiration, amelioration of insulin resistance, and suppression of fibrosis.

Characterization of Striga-Resistant Yellow-Orange Maize Hybrids for Bioactive, Carbohydrate, and Pasting Properties

Understanding the bioactive constituents and physicochemical components in cereals can provide insights into their potential health benefits and food applications. This study evaluated some bioactive constituents, carbohydrate profiles and pasting properties of 16 Striga-resistant hybrids, with yellow-orange kernel color and semi-flint to flint kernel texture, grown in two replications at two field locations in Nigeria. Carotenoids were quantified using HPLC, while other analyses were carried out using standard laboratory methods. The ranges of major carotenoids (μg/g) across the two locations varied from 2.6 to 9.6 for lutein, from 2.1 to 9.7 for zeaxanthin, from 0.8 to 2.9 for β-cryptoxanthin, from 1.4 to 4.1 for β-carotene; with total xanthophylls and provitamin A carotenoids (pVAC) ranging from 5.4 to 17.1 and 1.4 to 4.1 μg/g, respectively. Tannins content ranged from 2.1 to 7.3 mg/g, while phytate ranged from 0.4 to 7.1%. Starch, free sugar, amylose and amylopectin ranged from 40.1 to 88.9%, 1.09 to 6.5%, 15.0 to 34.1%, and 65.9 to 85.0%, respectively. Peak and final viscosities ranged from 57.8 to 114.9 and 120.3 to 261.6 Rapid Visco Units (RVU), respectively. Total xanthophylls, β-carotene, tannins, phytate, sugar, amylose and amylopectin levels, as well as peak and final viscosities, varied significantly (p &lt; 0.05) across the hybrids. Amylose was significantly correlated (p &lt; 0.05) with total xanthophylls, β-carotene, pVAC, phytate and pasting temperature (r = 0.3, 0.3, 0.4, 0.3, 0.3, respectively), but starch significantly correlated with tannins (r = 0.3). Hence, the Striga-resistant yellow-orange maize hybrids have a good combination of bioactive constituents, carbohydrate profile and pasting properties, which are partly influenced by hybrid.

A hypocaloric high-protein diet supplemented with β-cryptoxanthin improves non-alcoholic fatty liver disease: a randomized controlled trial

Background

Despite promising animal data, there is no randomized controlled trial (RCT) on the effects of high protein (HP)-diet and/or β-cryptoxanthin in non-alcoholic fatty liver disease (NAFLD). Aims: Safety and efficacy assessment of a hypocaloric HP-diet supplemented with β-cryptoxanthin in NAFLD.

Methods

Ninety-two Iranian NAFLD outpatients were recruited for this 12-week, single-center, parallel-group, double-blind RCT and randomized into 4 arms (n = 23): HP-diet and β-cryptoxanthin (hypocaloric HP-diet + β-cryptoxanthin), HP-diet (hypocaloric HP-diet + placebo), β-cryptoxanthin (standard hypocaloric diet + β-cryptoxanthin), and control (standard hypocaloric diet + placebo). Serum levels of liver enzymes and grade of hepatic steatosis were assessed at baseline and study endpoint as outcome measures.

Results

In the intention-to-treat population (N = 92), HP-diet and β-cryptoxanthin group experienced greater 12-week reductions in serum levels of liver enzymes than control group (mean difference for alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and gamma-glutamyl transferase: − 27.2, − 7.2, − 39.2, and − 16.3 IU/L, respectively; all p < 0.010). Clinical remission rate (achieving grade 0 hepatic steatosis) in HP-diet and β-cryptoxanthin group (82.6%) was also higher than other groups (13.0%, 17.4%, and 0.0% in HP-diet, β-cryptoxanthin, and control groups, respectively; p < 0.001). Sixteen patients reported minor adverse events.

Conclusion

A hypocaloric HP-diet supplemented with β-cryptoxanthin safely and efficaciously improves NAFLD.

Trial registration number

This trial was registered at https://www.irct.ir as IRCT2017060210181N10.

The Gut Microbiota and Its Metabolites, Novel Targets for Treating and Preventing Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent metabolic disorders worldwide, along with obesity and type 2 diabetes. NAFLD involves a series of liver abnormalities from simple hepatic steatosis to non-alcoholic steatohepatitis, which can ultimately lead to liver cirrhosis and cancer. The gut-liver axis plays an important role in the development of NAFLD, which depends mainly on regulation of the gut microbiota and its bacterial products. These intestinal bacterial species and their metabolites, including bile acids, tryptophan catabolites, and branched-chain amino acids, regulate adipose tissue and intestinal homeostasis and contribute to the pathogenesis of NAFLD/non-alcoholic steatohepatitis. In this review, the current evidence regarding the key role of the gut microbiota and its metabolites in the pathogenesis and development of NAFLD is highlighted, and the advances in the progression and applied prospects of gut microbiota-targeted dietary and exercise therapies is also discussed.

Kupffer Cells in Non-alcoholic Fatty Liver Disease: Friend or Foe?

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing all around the world and it may become the primary cause of terminal liver disease in adults and children in the next few decades. However, the pathogenesis of NAFLD is complex, and the Food and Drug Administration (FDA) has not approved any drugs for its treatment. Kupffer cells are the key cells regulating immunity in the liver, and the effect of their unique polarization on NAFLD has received increasing attention. Kupffer cells mainly reside in the lumen of hepatic sinusoids and account for 80% to 90% of colonized macrophages in the human body. They are phagocytic cells with the capacity for self-renewal that rarely migrate from their niche in the liver, and play a crucial role in regulating and maintaining homeostasis. Upon liver damage, Kupffer cells will be activated, releasing a good deal of inflammatory cytokines and chemokines. This review summarizes the multiple roles of Kupffer cells in the pathogenesis of NAFLD, the role of infiltrating macrophages in the pathogenesis of NAFLD is also briefly discussed, and aims to provide a theoretical basis for designing an NAFLD treatment strategy with Kupffer cells as the therapeutic target.

Correlation of plasma metabolites with glucose and lipid fluxes in human insulin resistance

OBJECTIVE

Insulin resistance develops prior to the onset of overt type 2 diabetes, making its early detection vital. Direct accurate evaluation is currently only possible with complex examinations like the stable isotope-based hyperinsulinemic euglycemic clamp (HIEC). Metabolomic profiling enables the detection of thousands of plasma metabolites, providing a tool to identify novel biomarkers in human obesity.

DESIGN

Liquid chromatography mass spectrometry-based untargeted plasma metabolomics was applied in 60 participants with obesity with a large range of peripheral insulin sensitivity as determined via a two-step HIEC with stable isotopes [6,6-2H2]glucose and [1,1,2,3,3-2H5]glycerol. This additionally enabled measuring insulin-regulated lipolysis, which combined with metabolomics, to the knowledge of this research group, has not been reported on before.

RESULTS

Several plasma metabolites were identified that significantly correlated with glucose and lipid fluxes, led by plasma (gamma-glutamyl)citrulline, followed by betaine, beta-cryptoxanthin, fructosyllysine, octanylcarnitine, sphingomyelin (d18:0/18:0, d19:0/17:0) and thyroxine. Subsequent machine learning analysis showed that a panel of these metabolites derived from a number of metabolic pathways may be used to predict insulin resistance, dominated by non-essential amino acid citrulline and its metabolite gamma-glutamylcitrulline.

CONCLUSION

This approach revealed a number of plasma metabolites that correlated reasonably well with glycemic and lipolytic flux parameters, measured using gold standard techniques. These metabolites may be used to predict the rate of glucose disposal in humans with obesity to a similar extend as HOMA, thus providing potential novel biomarkers for insulin resistance.

Lycopene prevents the progression of lipotoxicity-induced nonalcoholic steatohepatitis by decreasing oxidative stress in mice

Excessive fatty acid uptake-induced oxidative stress causes liver injury and the consecutive recruitment of inflammatory immune cells, thereby promoting the progression of simple steatosis to nonalcoholic steatohepatitis (NASH). Lycopene, the most effective singlet oxygen scavenger of the antioxidant carotenoids, has anti-inflammatory activity. Here, we investigated the preventive and therapeutic effects of lycopene in a lipotoxic model of NASH: mice fed a high-cholesterol and high-fat diet. Lycopene alleviated excessive hepatic lipid accumulation and enhanced lipolysis, decreased the proportion of M1-type macrophages/Kupffer cells, and activated stellate cells to improve hepatic inflammation and fibrosis, and subsequently reduced the recruitment of CD4⁺ and CD8⁺ T cells in the liver. Importantly, lycopene reversed insulin resistance, as well as hepatic inflammation and fibrosis, in pre-existing NASH. In parallel, lycopene decreased LPS-/IFN-γ-/TNFα-induced M1 marker mRNA levels in peritoneal macrophages, as well as TGF-β1-induced expression of fibrogenic genes in a stellate cell line, in a dose-dependent manner. These results were associated with decreased oxidative stress in cells, which might be mediated by the expression of NADPH oxidase subunits. In summary, lycopene prevented and reversed lipotoxicity-induced inflammation and fibrosis in NASH mice by reducing oxidative stress. Therefore, it might be a novel and promising treatment for NASH.

Metabolic Inflammation-A Role for Hepatic Inflammatory Pathways as Drivers of Comorbidities in Nonalcoholic Fatty Liver Disease?

Nonalcoholic fatty liver disease (NAFLD) is a global and growing health concern. Emerging evidence points toward metabolic inflammation as a key process in the fatty liver that contributes to multiorgan morbidity. Key extrahepatic comorbidities that are influenced by NAFLD are type 2 diabetes, cardiovascular disease, and impaired neurocognitive function. Importantly, the presence of nonalcoholic steatohepatitis and advanced hepatic fibrosis increase the risk for systemic comorbidity in NAFLD. Although the precise nature of the crosstalk between the liver and other organs has not yet been fully elucidated, there is emerging evidence that metabolic inflammation-in part, emanating from the fatty liver-is the engine that drives cellular dysfunction, cell death, and deleterious remodeling within various body tissues. This review describes several inflammatory pathways and mediators that have been implicated as links between NAFLD and type 2 diabetes, cardiovascular disease, and neurocognitive decline.

Carotenoids and carotenoid conversion products in adipose tissue biology and obesity: Pre-clinical and human studies

Antiobesity activities of carotenoids and carotenoid conversion products (CCPs) have been demonstrated in pre-clinical studies, and mechanisms behind have begun to be unveiled, thus suggesting these compounds may help obesity prevention and management. The antiobesity action of carotenoids and CCPs can be traced to effects in multiple tissues, notably the adipose tissues. Key aspects of the biology of adipose tissues appear to be affected by carotenoid and CCPs, including adipogenesis, metabolic capacities for energy storage, release and inefficient oxidation, secretory function, and modulation of oxidative stress and inflammatory pathways. Here, we review the connections of carotenoids and CCPs with adipose tissue biology and obesity as revealed by cell and animal intervention studies, studies addressing the role of endogenous retinoid metabolism, and human epidemiological and intervention studies. We also consider human genetic variability influencing carotenoid and vitamin A metabolism, particularly in adipose tissues, as a potentially relevant aspect towards personalization of dietary recommendations to prevent or manage obesity and optimize metabolic health. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Xanthine oxidase inhibition attenuates insulin resistance and diet-induced steatohepatitis in mice

Hyperuricemia drives the development of nonalcoholic fatty liver disease (NAFLD). Pharmacological inhibition of xanthine oxidase (XO), a rate-limiting enzyme for uric acid (UA) production, has been demonstrated to improve hepatic steatosis in diet-induced obese mice. However, it remains unclear whether inhibition of XO improves nonalcoholic steatohepatitis (NASH), a more advanced form of NAFLD, in terms of both liver inflammation and fibrosis. Here, we investigated the effects of febuxostat and allopurinol, two XO inhibitors clinically used for gout, on a mouse model of NASH. Furthermore, we conducted a single-arm, open-label intervention study with febuxostat for NAFLD patients with hyperuricemia. Despite a similar hypouricemic effect of the XO inhibitors on blood UA level, febuxostat, but not allopurinol, significantly decreased hepatic XO activity and UA levels in the NASH model mice. These reductions in hepatic XO activity and UA levels were accompanied by attenuation of insulin resistance, lipid peroxidation, and classically activated M1-like macrophage accumulation in the liver. Furthermore, in NAFLD patients with hyperuricemia, treatment with febuxostat for 24 weeks decreased the serum UA level, accompanied by reductions in the serum levels of liver enzymes, alanine aminotransferase and aspartate aminotransferase. XO may represent a promising therapeutic target in NAFLD/NASH, especially in patients with hyperuricemia.

Anti-stress Effect of β-Cryptoxanthin in Satsuma Mandarin Orange on Females

Beta-cryptoxanthin (β-CRX, (3R)-β, β-caroten-3-ol) is an oxygenated carotenoid and a potent antioxidant that is abundant in Satsuma mandarin orange (Citrus unshiu MARC.), which is the most popular fruit in Japan. Since our preliminary data suggested that the ingestion of β-CRX had an anti-stress effect in female participants, the effect was evaluated in another set of female participants. The study design was a double-blind group comparison and participants (n = 23) were randomly assigned to β-CRX-rich orange juice or placebo (β-CRX was removed from orange juice) groups. β-CRX or placebo juice (125 mL, after breakfast) were consumed from 1 week prior to pharmacy practice and continued for 5 d into the practice period. Salivary α-amylase activity (sAA), a marker of sympathetic nervous system activity, was significantly higher in the evening than in the morning in the placebo-group during pharmacy practice, but not in the β-CRX-group. This result supports the anti-stress effect of β-CRX. The dose-dependency of β-CRX was observed in male mice that were loaded with stress. These results indicate that the ingestion of β-CRX is helpful to reduce stress.

Carotenoids and fatty liver disease: Current knowledge and research gaps

Carotenoids form an important part of the human diet, consumption of which has been associated with many health benefits. With the growing global burden of liver disease, increasing attention has been paid on the possible beneficial role that carotenoids may play in the liver. This review focuses on carotenoid actions in non-alcoholic fatty liver disease (NAFLD), and alcoholic liver disease (ALD). Indeed, many human studies have suggested an association between decreased circulating levels of carotenoids and increased incidence of NAFLD and ALD. The literature describing supplementation of individual carotenoids in rodent models of NAFLD and ALD is reviewed, with particular attention paid to β-carotene and lycopene, but also including β-cryptoxanthin, lutein, zeaxanthin, and astaxanthin. The effect of beta-carotene oxygenase 1 and 2 knock-out mice on hepatic lipid metabolism is also discussed. In general, there is evidence to suggest that carotenoids have beneficial effects in animal models of both NAFLD and ALD. Mechanistically, these benefits may occur via three possible modes of action: 1) improved hepatic antioxidative status broadly attributed to carotenoids in general, 2) the generation of vitamin A from β-carotene and β-cryptoxanthin, leading to improved hepatic retinoid signaling, and 3) the generation of apocarotenoid metabolites from β-carotene and lycopene, that may regulate hepatic signaling pathways. Gaps in our knowledge regarding carotenoid mechanisms of action in the liver are highlighted throughout, and the review ends by emphasizing the importance of dose effects, mode of delivery, and mechanism of action as important areas for further study. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Pirfenidone prevents and reverses hepatic insulin resistance and steatohepatitis by polarizing M2 macrophages

Nonalcoholic steatohepatitis (NASH) is associated with lipotoxic liver injury, leading to insulin resistance, inflammation, and fibrosis. Despite its increased global incidence, very few promising treatments for NASH are available. Pirfenidone is an antifibrotic agent used to treat pulmonary fibrosis; it suppresses the pulmonary influx of T cells and macrophages. Here, we investigated the effect of pirfenidone in a mouse model of lipotoxicity-induced NASH via a high-cholesterol and high-fat diet. After 12 weeks of feeding, pirfenidone administration attenuated excessive hepatic lipid accumulation and peroxidation by reducing the expression of genes related to lipogenesis and fatty acid synthesis and enhancing the expression of those related to fatty acid oxidation. Flow cytometry indicated that pirfenidone reduced the number of total hepatic macrophages, particularly CD11c⁺CD206^-(M1)-type macrophages, increased the number of CD11c^-CD206⁺(M2)-type macrophages, and subsequently reduced T-cell numbers, which helped improve insulin resistance and steatohepatitis. Moreover, pirfenidone downregulated the lipopolysaccharide (LPS)-induced mRNA expression of M1 marker genes and upregulated IL-4-induced M2 marker genes in a dose-dependent manner in RAW264.7 macrophages. Importantly, pirfenidone reversed insulin resistance, hepatic inflammation, and fibrosis in mice with pre-existing NASH. These findings suggest that pirfenidone is a potential candidate for the treatment of NASH.

Dietary β-Cryptoxanthin Inhibits High-Refined Carbohydrate Diet-Induced Fatty Liver via Differential Protective Mechanisms Depending on Carotenoid Cleavage Enzymes in Male Mice

BACKGROUND

β-Cryptoxanthin (BCX), a provitamin A carotenoid shown to protect against nonalcoholic fatty liver disease (NAFLD), can be cleaved by β-carotene-15,15'-oxygenase (BCO1) to generate vitamin A, and by β-carotene-9',10'-oxygenase (BCO2) to produce bioactive apo-carotenoids. BCO1/BCO2 polymorphisms have been associated with variations in plasma carotenoid amounts in both humans and animals.

OBJECTIVES

We investigated whether BCX feeding inhibits high refined-carbohydrate diet (HRCD)-induced NAFLD, dependent or independent of BCO1/BCO2.

METHODS

Six-week-old male wild-type (WT) and BCO1-/-/BCO2-/- double knockout (DKO) mice were randomly fed HRCD (66.5% of energy from carbohydrate) with or without BCX (10 mg/kg diet) for 24 wk. Pathological and biochemical variables were analyzed in the liver and mesenteric adipose tissues (MATs). Data were analyzed by 2-factor ANOVA.

RESULTS

Compared to their respective HRCD controls, BCX reduced hepatic steatosis severity by 33‒43% and hepatic total cholesterol by 43‒70% in both WT and DKO mice (P < 0.01). Hepatic concentrations of BCX, but not retinol and retinyl palmitate, were 33-fold higher in DKO mice than in WT mice (P < 0.001). BCX feeding increased the hepatic fatty acid oxidation protein peroxisome proliferator-activated receptor-α, and the cholesterol efflux gene ATP-binding cassette transporter5, and suppressed the lipogenesis gene acetyl-CoA carboxylase 1 (Acc1) in the MAT of WT mice but not DKO mice (P < 0.05). BCX feeding decreased the hepatic lipogenesis proteins ACC and stearoyl-CoA desaturase-1 (3-fold and 5-fold) and the cholesterol synthesis genes 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase and HMG-CoA synthase 1 (2.7-fold and 1.8-fold) and increased the cholesterol catabolism gene cholesterol 7α-hydroxylase (1.9-fold) in the DKO but not WT mice (P < 0.05). BCX feeding increased hepatic protein sirtuin1 (2.5-fold) and AMP-activated protein kinase (9-fold) and decreased hepatic farnesoid X receptor protein (80%) and the inflammatory cytokine gene Il6 (6-fold) in the MAT of DKO mice but not WT mice (P < 0.05).

CONCLUSION

BCX feeding mitigates HRCD-induced NAFLD in both WT and DKO mice through different mechanisms in the liver-MAT axis, depending on the presence or absence of BCO1/BCO2.

Nutritional Importance of Carotenoids and Their Effect on Liver Health: A Review

The consumption of carotenoids has beneficial effects on health, reducing the risk of certain forms of cancer, cardiovascular diseases, and macular degeneration, among others. The mechanism of action of carotenoids has not been clearly identified; however, it has been associated with the antioxidant capacity of carotenoids, which acts against reactive oxygen species and inactivating free radicals, although it has also been shown that carotenoids modulate gene expression. Dietary carotenoids are absorbed and accumulated in the liver and other organs, where they exert their beneficial effects. In recent years, it has been described that the intake of carotenoids can significantly reduce the risk of suffering from liver diseases, such as non-alcoholic fatty liver disease (NAFLD). This disease is characterized by an imbalance in lipid metabolism producing the accumulation of fat in the hepatocyte, leading to lipoperoxidation, followed by oxidative stress and inflammation. In the first phases, the main treatment of NAFLD is to change the lifestyle, including dietary habits. In this sense, carotenoids have been shown to have a hepatoprotective effect due to their ability to reduce oxidative stress and regulate the lipid metabolism of hepatocytes by modulating certain genes. The objective of this review was to provide a description of the effects of dietary carotenoids from fruits and vegetables on liver health.

Anti-Obesity Effect of Carotenoids: Direct Impact on Adipose Tissue and Adipose Tissue-Driven Indirect Effects

This review summarizes current knowledge on the biological relevance of carotenoids and some of their metabolites in obesity management. The relationship between carotenoids and obesity is considered in clinical studies and in preclinical studies. Adipose tissue is a key organ in obesity etiology and the main storage site for carotenoids. We thus first describe carotenoid metabolism in adipocyte and adipose tissue and the effects of carotenoids on biological processes in adipose tissue that may be linked to obesity management in in vitro and preclinical studies. It is also now well established that the brain is strongly involved in obesity processes. A section is accordingly devoted to the potential effect of carotenoids on obesity via their direct and/or adipose tissue-driven indirect biological effects on the brain.

Health Benefits of Carotenoids: A Role of Carotenoids in the Prevention of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases with a prevalence of ~25% worldwide. NAFLD includes simple hepatic steatosis, non-alcoholic steatohepatitis, fibrosis, and cirrhosis, which can further progress to hepatocellular carcinoma. Therefore, effective strategies for the prevention of NAFLD are needed. The pathogenesis of NAFLD is complicated due to diverse injury insults, such as fat accumulation, oxidative stress, inflammation, lipotoxicity, and apoptosis, which may act synergistically. Studies have shown that carotenoids, a natural group of isoprenoid pigments, prevent the development of NAFLD by exerting antioxidant, lipid-lowering, anti-inflammatory, anti-fibrotic, and insulin-sensitizing properties. This review summarizes the protective action of carotenoids, with primary focuses on astaxanthin, lycopene, β-carotene, β-cryptoxanthin, lutein, fucoxanthin, and crocetin, against the development and progression of NAFLD.

Heterogeneous macrophages: Supersensors of exogenous inducing factors

As heterogeneous immune cells, macrophages mount effective responses to various internal and external changes during disease progression. Macrophage polarization, rather than macrophage heterogenization, is often used to describe the functional differences between macrophages. While macrophage polarization partially contributes to heterogeneity, it does not completely explain the concept of macrophage heterogeneity. At the same time, there are abundant and sophisticated endogenous and exogenous substances that can affect macrophage heterogeneity. While the research on endogenous factors has been systematically reviewed, the findings on exogenous factors have not been well summarized. Hence, we reviewed the characteristics and inducing factors of heterogeneous macrophages to reveal their functional plasticity as well as their targeting manoeuvreability. In the process of constructing and analysing a network organized by disease-related cells and molecules, paying more attention to heterogeneous macrophages as mediators of this network may help to explore a novel entry point for early prevention of and intervention in disease.

Bioprospecting the Solar Panel Microbiome: High-Throughput Screening for Antioxidant Bacteria in a Caenorhabditis elegans Model

Microbial communities that are exposed to sunlight typically share a series of adaptations to deal with the radiation they are exposed to, including efficient DNA repair systems, pigment production and protection against oxidative stress, which makes these environments good candidates for the search of novel antioxidant microorganisms. In this research project, we isolated potential antioxidant pigmented bacteria from a dry and highly-irradiated extreme environment: solar panels. High-throughput in vivo assays using Caenorhabditis elegans as an experimental model demonstrated the high antioxidant and ultraviolet-protection properties of these bacterial isolates that proved to be rich in carotenoids. Our results suggest that solar panels harbor a microbial community that includes strains with potential applications as antioxidants.

β-Cryptoxanthin Reduces Body Fat and Increases Oxidative Stress Response in Caenorhabditis elegans Model

β-Cryptoxanthin (BCX) is a major dietary pro-vitamin A carotenoid, found mainly in fruits and vegetables. Several studies showed the beneficial effects of BCX on different aspects of human health. In spite of the evidence, the molecular mechanisms of action of BCX need to be further investigated. The Caenorhabditis elegans model was used to analyze in vivo the activity of BCX on fat reduction and protection to oxidative stress. Dose-response assays provided evidence of the efficacy of BCX at very low dose (0.025 µg/mL) (p < 0.001) on these processes. Moreover, a comparative analysis with other carotenoids, such as lycopene and β-carotene, showed a stronger effect of BCX. Furthermore, a transcriptomic analysis of wild-type nematodes supplemented with BCX revealed upregulation of the energy metabolism, response to stress, and protein homeostasis as the main metabolic targets of this xanthophyll. Collectively, this study provides new in vivo evidence of the potential therapeutic use of BCX in the prevention of diseases related to metabolic syndrome and aging.

Empagliflozin reverses obesity and insulin resistance through fat browning and alternative macrophage activation in mice fed a high-fat diet

OBJECTIVE

We reported previously that empagliflozin-a sodium-glucose cotransporter (SGLT) 2 inhibitor-exhibited preventive effects against obesity. However, it was difficult to extrapolate these results to human subjects. Here, we performed a therapeutic study, which is more relevant to clinical situations in humans, to investigate antiobesity effects of empagliflozin and illustrate the mechanism underlying empagliflozin-mediated enhanced fat browning in obese mice.

RESEARCH DESIGN AND METHODS

After 8 weeks on a high-fat diet (HFD), C57BL/6J mice exhibited obesity, accompanied by insulin resistance and low-grade chronic inflammation. Cohorts of obese mice were continued on the HFD for an additional 8-week treatment period with or without empagliflozin.

RESULTS

Treatment with empagliflozin for 8 weeks markedly increased glucose excretion in urine, and suppressed HFD-induced weight gain, insulin resistance and hepatic steatosis. Notably, empagliflozin enhanced oxygen consumption and carbon dioxide production, leading to increased energy expenditure. Consistently, the level of uncoupling protein 1 expression was increased in both brown and white (WAT) adipose tissues of empagliflozin-treated mice. Furthermore, empagliflozin decreased plasma levels of interleukin (IL)-6 and monocyte chemoattractant protein-1, but increased plasma levels of IL-33 and adiponectin in obese mice. Finally, we found that empagliflozin reduced M1-polarized macrophage accumulation, while inducing the anti-inflammatory M2 phenotype of macrophages in the WAT and liver, thereby attenuating obesity-related chronic inflammation.

CONCLUSIONS

Treatment with empagliflozin attenuated weight gain by increasing energy expenditure and adipose tissue browning, and alleviated obesity-associated inflammation and insulin resistance by alternative macrophage activation in the WAT and liver of obese mice.

Role of vitamin E in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide. NAFLD manifests as hepatic lipid accumulation, insulin resistance, and inflammation, and can progress to nonalcoholic steatohepatitis (NASH) and cirrhosis. However, the underlying mechanisms of NAFLD, including those that drive its progression, are unclear. Both liver-resident (Kupffer cells) and recruited macrophages play a crucial role in the development of insulin resistance and NASH. Therefore, NALFD could potentially be ameliorated by modifying the polarization of macrophages/Kupffer cells. Reactive oxygen species induce oxidative stress, which is implicated in the progression of NASH. Micronutrients, including vitamins, are potent antioxidants that exert anti-inflammatory effects, and are used in the treatment of NAFLD. We review here the molecular mechanisms of the pathogenesis of NAFLD and the potential utility of vitamin E in its prevention and/or treatment. © 2018 IUBMB Life, 71(4):516-522, 2019.

Chemokines and Chemokine Receptors in the Development of NAFLD

Chemokines are chemo-attractants for leukocyte trafficking, growth, and activation in injured and inflammatory tissues. The chemokine system is comprised of 50 chemokine ligands and 20 cognate chemokine receptors. In the context of liver diseases, leukocytes, hepatocytes, hepatic stellate cells, endothelial cells, and vascular smooth muscle cells are capable of producing chemokines. Chemokine receptors are typically expressed in various leukocyte subsets. Given that inflammation is a critical factor for the transition from simple steatosis to non-alcoholic steatohepatitis (NASH), and fibrosis, the chemokine system may play a prominent role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Indeed, accumulating evidence shows elevated expression of chemokines and their receptors in the livers of obese patients with advanced steatosis and NASH. This chapter will discuss the underlying molecular mechanisms and the therapeutic potential of the chemokine systems in the pathogenesis of NAFLD. Among chemokines, we will highlight CCL2, CCL5, CXCL8-10, CX3CL1, and CXCL16 as pivotal mediators in the development of steatosis, NASH, and fibrosis.