Lipid-lowering agents in the management of nonalcoholic fatty liver disease

Recent advancements in the structural exploration of TGR5 agonists for diabetes treatment

TGR5, a receptor that interacts with bile acids on cell surfaces, has become a promising therapeutic target for type II diabetes due to its ability to regulate energy expenditure and blood sugar levels. While several TGR5 agonists have been identified, only a few are currently in clinical trials. This article reviews the promising TGR5 agonists discovered in recent years, highlighting the chemical structure and pharmacological profile of the most effective compounds. With the limited number of effective drugs available for treating type II diabetes, the search for a potent TGR5 agonist with high efficacy and fewer side effects continues. The goal of this article is to provide an overview of the latest advancements in TGR5 agonists and offer insights for the future development of novel, potent TGR5 agonists for diabetes treatment. A noteworthy aspect addressed in the discussion is the common side effect associated with TGR5 agonist treatment - gallbladder filling. The review also explores potential strategies to mitigate this side effect, with the goal of improving the overall safety and tolerability of TGR5-targeted therapies.

Statins on nonalcoholic fatty liver disease: A systematic review and meta-analysis of 14 RCTs

BACKGROUND

The prevalence of nonalcoholic fatty liver disease (NAFLD) is rising rapidly in the world. Our aim is to investigate the efficacy and safety of statins in the treatment of NAFLD.

METHODS

This study was conducted by searching The National Library of Medicine, Cochrane Library, China National Knowledge Infrastructure, Web of Science, and Wanfang Data Knowledge Service Platform databases. Literature data are expressed as mean difference (MD) and 95% confidence intervals (CIs) or relative risk and 95% CI. For I2 > 50% trials, random effect model is used for statistical analysis, otherwise fixed effect model is used.

RESULTS

Fourteen studies are selected for this meta-analysis, which includes totally 534 patients in the treatment group and 527 patients in the control group. As a result, 5 studies show that the total effective rate of the treatment group is 17% higher than that of the control group (Z = 2.11, relative risk = 1.17, 95% CI: [1.01-1.35]). Twelve studies show that alanine aminotransferase levels of the experimental group are lower than that of the control group (Z = 2.63, P = .009, MD = -5.53, 95% CI: [-9.64 to -1.41]). Eleven studies show that aspartate transaminase levels of the experimental group are lower than that of the control group (Z = 2.01, P = .04, MD = -3.43, 95% CI: [-6.77 to -0.08]). Six studies show that alkaline phosphatase levels of the experimental group are lower than that of the control group (Z = 0.79, P = .43, MD = -3.46, 95% CI: [-12.08 to 5.16]). Eight studies show that gamma-glutamyl transpeptidase levels of the experimental group are lower than that of the control group (Z = 2.04, P = .04, MD = -4.05, 95% CI: [-7.96 to -0.15]). Thirteen studies show that triglyceride levels of the experimental group are lower than that of the control group (Z = 4.15, P < .0001, MD = -0.94, 95% CI: [-1.39 to -0.50]). Eleven studies show that the total cholesterol levels of the experimental group are lower than that of the control group (Z = 5.42, P < .00001, MD = -1.51, 95% CI: [-2.05 to -0.96]). Seven studies show that low-density lipoprotein-cholesterol levels of the experimental group are lower than that of the control group (Z = 5.00, P < .00001, MD = -0.85, 95% CI: [-1.18 to -0.52]).

CONCLUSION

Statins can significantly reduce liver biochemical indicators in patients with NAFLD.

Regulation of cholesterol homeostasis in health and diseases: from mechanisms to targeted therapeutics

Disturbed cholesterol homeostasis plays critical roles in the development of multiple diseases, such as cardiovascular diseases (CVD), neurodegenerative diseases and cancers, particularly the CVD in which the accumulation of lipids (mainly the cholesteryl esters) within macrophage/foam cells underneath the endothelial layer drives the formation of atherosclerotic lesions eventually. More and more studies have shown that lowering cholesterol level, especially low-density lipoprotein cholesterol level, protects cardiovascular system and prevents cardiovascular events effectively. Maintaining cholesterol homeostasis is determined by cholesterol biosynthesis, uptake, efflux, transport, storage, utilization, and/or excretion. All the processes should be precisely controlled by the multiple regulatory pathways. Based on the regulation of cholesterol homeostasis, many interventions have been developed to lower cholesterol by inhibiting cholesterol biosynthesis and uptake or enhancing cholesterol utilization and excretion. Herein, we summarize the historical review and research events, the current understandings of the molecular pathways playing key roles in regulating cholesterol homeostasis, and the cholesterol-lowering interventions in clinics or in preclinical studies as well as new cholesterol-lowering targets and their clinical advances. More importantly, we review and discuss the benefits of those interventions for the treatment of multiple diseases including atherosclerotic cardiovascular diseases, obesity, diabetes, nonalcoholic fatty liver disease, cancer, neurodegenerative diseases, osteoporosis and virus infection.

Management of Hypercholesterolemia Through Dietary ß-glucans–Insights From a Zebrafish Model

Consumption of lipid-rich foods can increase the blood cholesterol content. β-glucans have hypocholesterolemic effect. However, subtle changes in their molecular branching can influence bioactivity. Therefore, a comparative investigation of the cholesterol-lowering potential of two β-glucans with different branching patterns and a cholesterol-lowering drug, namely simvastatin was undertaken employing the zebrafish (Danio rerio) model of diet-induced hypercholesterolemia. Fish were allocated to 5 dietary treatments; a control group, a high cholesterol group, two β-glucan groups, and a simvastatin group. We investigated plasma total cholesterol, LDL and HDL cholesterol levels, histological changes in the tissues, and explored intestinal transcriptomic changes induced by the experimental diets. Dietary cholesterol likely caused the suppression of endogenous cholesterol biosynthesis, induced dysfunction of endoplasmic reticulum and mitochondria, and altered the histomorphology of the intestine. The two β-glucans and simvastatin significantly abated the rise in plasma cholesterol levels and restored the expression of specific genes to alleviate the endoplasmic reticulum-related effects induced by the dietary cholesterol. Furthermore, the distinct patterns of transcriptomic changes in the intestine elicited by the oat and microalga β-glucans impacted processes such as fatty acid metabolism, protein catabolic processes, and nuclear division. Oat and microalgal β-glucans also altered the pattern of lipid deposition in the liver. Our study provides insights into the effectiveness of different β-glucans to alleviate dysfunctions in lipid metabolism caused by dietary cholesterol.

From Liver Fat to Cancer: Perils of the Western Diet

Hepatocellular carcinoma (HCC), the most common type of primary liver cancer provides the prototypical example of an obesity-related cancer. The obesity epidemic gave rise to an enormous increase in the incidence of non-alcoholic fatty liver disease (NAFLD), a condition that affects one third of American adults. In about 20% of these individuals, simple liver steatosis (hepatosteatosis) progresses to non-alcoholic steatohepatitis (NASH) characterized by chronic liver injury, inflammation, and fibrosis. In addition to liver failure, NASH greatly increases the risk of HCC. Here we discuss the metabolic processes that control the progression from NAFLD to NASH and from NASH to HCC, with a special emphasis on the role of free-non-esterified cholesterol in the process.

Changes in the Epidemiology of Hepatobiliary Disease Complicating Type 2 Diabetes over 25 Years: The Fremantle Diabetes Study

OBJECTIVE

To determine whether the incidence/outcome of hepatobiliary disease (HBD) has increased over recent decades in community-based Australians with and without type 2 diabetes (T2D).

METHODS

Longitudinal data from the Fremantle Diabetes Study Phase I (FDS1; recruitment 1993-1996; n = 1291 with T2D) and Phase II (FDS2; 2008-2011; n = 1509) were analyzed. Participants with T2D from both Phases were age-, sex-, and postcode-matched 1:4 to people without diabetes. Incident HBD and associated mortality were ascertained from hospitalization, cancer registration, and/or death certification codes. Incidence rates (IRs) and IR ratios (IRRs) for those with versus without diabetes in FDS1 and FDS2 were calculated.

RESULTS

HBD IRs for people without diabetes did not change between Phases. The IRR (95% CI) for people with T2D in FDS2 versus FDS1 was 1.30 (1.01-1.68) with the highest IRRs in participants aged <65 years. Non-alcoholic fatty liver disease/steatohepatitis (NAFLD/NASH) events were 54% greater in FDS2 than FDS1 in the presence of greater abdominal adiposity. NAFLD/NASH was coded in one in 11 HBD events in FDS2 and in 10% of HBD deaths (<4% of total mortality).

CONCLUSIONS

HBD is more frequent in people with versus without T2D and this discrepancy is increasing. Hospitalizations/deaths due to NAFLD/NASH remain uncommon.

Nonalcoholic Steatohepatitis and Endpoints in Clinical Trials

Nonalcoholic fatty liver disease (NAFLD) is now the leading cause of liver disease in developed countries, and the rates of NAFLD continue to rise in conjunction with the obesity pandemic. While the majority of patients with isolated steatosis generally have a benign course, a diagnosis of nonalcoholic steatohepatitis (NASH) carries a significantly higher risk for progression of disease, cirrhosis, and death. Pharmacologic therapeutic interventions in NASH have largely proven to be ineffective or unappealing due to long-term side-effect profiles, and the majority of patients cannot achieve or sustain targeted weight loss goals, necessitating an urgent need for therapeutic trials and drug development. The complex molecular mechanisms leading to NASH and the long duration of time to develop complications of disease are challenges to developing meaningful clinical endpoints. Because of these challenges, surrogate endpoints that are linked to all-cause mortality, liver-related death, and complications of cirrhosis are much more likely to be beneficial in the majority of patients.

The adipokines in the pathogenesis and treatment of nonalcoholic fatty liver disease

Insulin resistance, abdominal obesity, and inflammation play important roles in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Several adipokines, particularly adiponectin but also leptin, resistin, irisin, ghrelin, and visfatin modulate these pathogenetic mechanisms and appear to play a role in the development of hepatic steatosis and the progression to steatohepatitis and cirrhosis. Accordingly, these adipokines might represent attractive targets in patients with NAFLD. Notably, both lifestyle changes and many pharmacological agents that are used in the management of NAFLD, particularly pioglitazone and statins, exert favorable effects on adipokine levels. However, it is unclear whether these effects play a role in the improvement in liver histology. Therefore, mechanistic studies are needed to clarify the contribution of changes in adipokine levels to the effects of these interventions on hepatic steatosis, inflammation, and fibrosis. In parallel, the development of novel agents that specifically target adipokine levels might offer additional insights into the potential role of adipokines as therapeutic targets in NAFLD. Hippokratia 2016, 20(4): 259-263.

Non-alcoholic fatty liver disease and dyslipidemia: An update

Non-alcoholic fatty liver (NAFLD) is the most common liver disease worldwide, progressing from simple steatosis to necroinflammation and fibrosis (leading to non-alcoholic steatohepatitis, NASH), and in some cases to cirrhosis and hepatocellular carcinoma. Inflammation, oxidative stress and insulin resistance are involved in NAFLD development and progression. NAFLD has been associated with several cardiovascular (CV) risk factors including obesity, dyslipidemia, hyperglycemia, hypertension and smoking. NAFLD is also characterized by atherogenic dyslipidemia, postprandial lipemia and high-density lipoprotein (HDL) dysfunction. Most importantly, NAFLD patients have an increased risk for both liver and CV disease (CVD) morbidity and mortality. In this narrative review, the associations between NAFLD, dyslipidemia and vascular disease in NAFLD patients are discussed. NAFLD treatment is also reviewed with a focus on lipid-lowering drugs. Finally, future perspectives in terms of both NAFLD diagnostic biomarkers and therapeutic targets are considered.

Intestinally-targeted TGR5 agonists equipped with quaternary ammonium have an improved hypoglycemic effect and reduced gallbladder filling effect

TGR5 activation of enteroendocrine cells increases glucagon-like peptide 1 (GLP-1) release, which maintains glycemic homeostasis. However, TGR5 activation in the gallbladder and heart is associated with severe side effects. Therefore, intestinally-targeted TGR5 agonists were suggested as potential hypoglycemic agents with minimal side effects. However, until now no such compounds with robust glucose-lowering effects were reported, especially in diabetic animal models. Herein, we identify a TGR5 agonist, 26a, which was proven to be intestinally-targeted through pharmacokinetic studies. 26a was used as a tool drug to verify the intestinally-targeted strategy. 26a displayed a robust and long-lasting hypoglycemic effect in ob/ob mice (once a day dosing (QD) and 18-day treatment) owing to sustained stimulation of GLP-1 secretion, which suggested that robust hypoglycemic effect could be achieved with activation of TGR5 in intestine alone. However, the gallbladder filling effect of 26a was rather complicated. Although the gallbladder filling effect of 26a was decreased in mice after once a day dosing, this side effect was still not eliminated. To solve the problem above, several research strategies were raised for further optimization.

Cardiovascular risk assessment in the treatment of nonalcoholic steatohepatitis: a secondary analysis of the MOZART trial

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is associated with increased cardiovascular risk and mortality. No US Food and Drug Administration (FDA) approved therapies for NASH are available; clinical trials to date have not yet systematically assessed for changes in cardiovascular risk. This study examines the prospective utility of cardiovascular risk assessments, the Framingham risk score (FRS) and coronary artery calcium (CAC) score, as endpoints in a NASH randomized clinical trial, and assesses whether histologic improvements lead to lower cardiovascular risk.

METHODS

Secondary analysis of a 24-week randomized, double-blind, placebo-controlled trial (MOZART) in which 50 biopsy-proven NASH patients received oral ezetimibe 10 mg daily (n = 25) versus placebo (n = 25). Biochemical profiling, FRS, CAC scores, liver biopsies were obtained at baseline and endpoint.

RESULTS

Ezetimibe improved FRS whereas placebo did not (4.4 ± 6.2 to 2.9 ± 4.8, p = 0.038; 3.0 ± 4.4 to 2.9 ± 4.2, p = 0.794). CAC scores did not change with ezetimibe or placebo (180.4 ± 577.2 to 194.1 ± 623.9, p = 0.293; 151.4 ± 448.9 to 183.3 ± 555.7, p = 0.256). Ezetimibe improved FRS and CAC scores in more patients than placebo (48% versus 23%, p = 0.079, and 21% versus 0%, p = 0.090, respectively), though not significantly. No differences were noted in cardiovascular risk scores among histologic responders versus nonresponders.

CONCLUSIONS

Ezetimibe improved FRS whereas placebo did not. FRS and CAC scores improved in a greater proportion of patients with ezetimibe; this trend did not reach significance. These findings indicate the utility and feasibility of monitoring cardiovascular risk in a NASH trial. The utility of CAC scores may be higher in trials of longer duration (⩾52 weeks) and with older patients (age ⩾45). ClinicalTrials.gov registration: NCT01766713.

Nonalcoholic fatty liver disease and statins

OBJECTIVE

Nonalcoholic fatty liver disease (NAFLD) is the most frequent cause of elevated transaminase levels and affects approximately one third of the general population. Patients with NAFLD are at increased risk for cardiovascular events, which represent the leading cause of death in this population. We discuss the safety and efficacy of statins in this population.

MATERIALS/METHODS

We reviewed the most recent literature on the safety of statins in patients with NAFLD and on their effects on liver histology and cardiovascular events.

RESULTS

It appears that statins can be safely administered to patients with NAFLD, including those with elevated transaminase levels (<3 times the upper limit of normal). Post-hoc analyses of randomized controlled trials also suggest that statins might reduce cardiovascular morbidity in this population. On the other hand, there are few and controversial data on the effects of statins on liver histology in patients with NAFLD.

CONCLUSIONS

Statins appear to be safe and might also reduce cardiovascular events in patients with NAFLD. Ongoing and future studies will clarify whether statins might also have a role in the treatment of NAFLD.

Effects on Liver Lipid Metabolism of the Naturally Occurring Dietary Flavone Luteolin-7-glucoside

Disruptions in whole-body lipid metabolism can lead to the onset of several pathologies such as nonalcoholic fatty liver disease (NAFLD) and cardiovascular diseases (CVDs). The present study aimed at elucidating the molecular mechanisms behind the lipid-lowering effects of the flavone luteolin-7-glucoside (L7G) which we previously showed to improve plasma lipid profile in rats. L7G is abundant in plant foods of Mediterranean diet such as aromatic plants used as herbs. Results show that dietary supplementation with L7G for one week induced the expression of peroxisome proliferator-activated receptor-alpha (PPAR-α) and of its target gene carnitine palmitoyl transferase 1 (CPT-1) in rat liver. L7G showed a tendency to decrease the hepatic expression of sterol regulatory element-binding protein-1 (SREBP-1), without affecting fatty acid synthase (FAS) protein levels. Although SREBP-2 and LDLr mRNA levels did not change, the expression of HMG CoA reductase (HMGCR) was significantly repressed by L7G. L7G also inhibited this enzyme's in vitro activity in a dose dependent manner, but only at high and not physiologically relevant concentrations. These results add new evidence that the flavone luteolin-7-glucoside may help in preventing metabolic diseases and clarify the mechanisms underlying the beneficial health effects of diets rich in fruits and vegetables.