How does coffee prevent liver fibrosis? Biological plausibility for recent epidemiological observations

Reassessing the Impact of Coffee Consumption on Liver Disease: Insights from a Large-Scale Cohort Study with IPTW Adjustment

Coffee consumption is globally widespread and has become a lifestyle habit. This study investigated coffee consumption and liver-related survival in a large cohort of 455,870 individuals with UK biobank, categorized into without steatosis, metabolic dysfunction-associated steatotic liver disease (MASLD), and MASLD and increased alcohol intake (MetALD). Inverse probability of treatment weighting (IPTW) adjusted for confounding variables was used, followed by Kaplan-Meier analysis. Moderate coffee consumption (1-2 cups per day) was associated with lower all-cause mortality across the entire cohort, without the steatosis, MASLD (p < 0.0001), and MetALD cohorts (p = 0.0047 for pre-IPTW, p = 0.027 for post-IPTW). Before IPTW adjustment, consuming one or more cups of coffee per day appeared to significantly reduce liver-related mortality in the overall (p = 0.015) and MASLD cohorts (p = 0.011). However, post-IPTW application, no significant differences in liver-related mortality were observed between the coffee intake groups (p = 0.778, 0.319, 0.564, 0.238 for each group). While increased coffee consumption initially seemed to reduce liver-related mortality, after IPTW adjustment, only all-cause mortality significantly decreased (p < 0.0001 and p = 0.027). These findings suggest that previous studies might have overestimated the favorable effect of coffee intake on chronic liver disease due to confounding factors.

Coffee, adenosine, and the liver

A variety of observational studies have demonstrated that coffee, likely acting through caffeine, improves health outcomes in patients with chronic liver disease. The primary pharmacologic role of caffeine is to act as an inhibitor of adenosine receptors. Because key liver cells express adenosine receptors linked to liver injury, regeneration, and fibrosis, it is plausible that the biological effects of coffee are explained by effects of caffeine on adenosinergic signaling in the liver. This review is designed to help the reader make sense of that hypothesis, highlighting key observations in the literature that support or dispute it.

Different Associations of Coffee Consumption with the Risk of Incident Metabolic Dysfunction-Associated Steatotic Liver Disease and Advanced Liver Fibrosis

Although coffee has a potential hepatoprotective effect, evidence of the relationship between coffee consumption and metabolic dysfunction-associated steatotic liver disease (MASLD) remains conflicting. There is limited evidence regarding the most appropriate coffee intake to prevent advanced liver fibrosis (ALF) in patients with MASLD. We investigated the effect of coffee consumption on MASLD and ALF among 5266 participants without MASLD and 1326 with MASLD but without ALF. Participants were grouped by coffee intake: non-consumers, >0 and <1 cups/day, ≥1 and <2 cups/day, and ≥2 cups/day. Over a median follow-up of 11.6 years for MASLD and 15.7 years for ALF, coffee consumption did not significantly affect the incidence of MASLD, with 2298 new cases observed. However, a notable inverse association was found with ALF risk in patients with MASLD among those consuming coffee ≥2 cups/day (adjusted HR 0.57, 95% CI: 0.37-0.90, p = 0.014), especially among those consuming coffee ≥2 and <3 cups/day (adjusted HR 0.51, 95% CI: 0.30-0.89, p = 0.018). This suggests a potential hepatoprotective effect of coffee, especially in preventing the progression of liver fibrosis in patients with MASLD. These findings propose that coffee consumption could be a simple and effective approach to mitigate the risk of ALF in individuals with MASLD.

Adenosine deaminase 2 produced by infiltrative monocytes promotes liver fibrosis in nonalcoholic fatty liver disease

Elevated circulating activity of adenosine deaminase 2 (ADA2) is associated with liver fibrosis in nonalcoholic fatty liver disease (NAFLD). In the liver of NAFLD patients, ADA2-positive portal macrophages are significantly associated with the degree of liver fibrosis. These liver macrophages are CD14- and CD16-positive and co-express chemokine receptors CCR2, CCR5, and CXCR3, indicating infiltrative monocyte origin. Human circulatory monocytes release ADA2 upon macrophage differentiation in vitro. When stimulated by recombinant human ADA2 (rhADA2), human monocyte-derived macrophages demonstrate upregulation of pro-inflammatory and pro-fibrotic genes, including PDGF-B, a key pro-fibrotic cytokine. This PDGF-B upregulation is reproduced by inosine, the enzymatic product of ADA2, but not adenosine, and is abolished by E359N, a loss-of-function mutation in ADA2. Finally, rhADA2 also stimulates PDGF-B production from Kupffer cells in primary human liver spheroids. Together, these data suggest that infiltrative monocytes promote fibrogenesis in NAFLD via ADA2-mediated autocrine/paracrine signaling culminating in enhanced PDGF-B production.

Effects of supplementation with main coffee components including caffeine and/or chlorogenic acid on hepatic, metabolic, and inflammatory indices in patients with non-alcoholic fatty liver disease and type 2 diabetes: a randomized, double-blind, placebo-controlled, clinical trial

Background

Non-alcoholic fatty liver disease (NAFLD) is much more frequent and more severe, including cirrhosis, hepatocellular carcinoma in patients with type 2 diabetes. Coffee is a complex beverage with hundreds of compounds whereas caffeine and chlorogenic acid are the most abundant bioactive compounds. The published epidemiological data demonstrating beneficial associations between all categories of coffee exposure and ranges of liver outcomes are rapidly growing; however, the main contributors and cause-effect relationships have not yet been elucidated. To address existing knowledge gaps, we sought to determine the efficacy and safety of 6 months chlorogenic acid and/or caffeine supplementation in patients with type 2 diabetes affected by NAFLD.

Methods

This trial was carried out at two Diabetes Centers to assess the effects of supplementation with daily doses of 200 mg chlorogenic acid, 200 mg caffeine, 200 mg chlorogenic acid plus 200 mg caffeine or placebo (starch) in patients with type 2 diabetes and NAFLD. The primary endpoint was reduction of hepatic fat and stiffness measured by FibroScan, and changes in serum hepatic enzymes and cytokeratin − 18 (CK-18) levels. Secondary endpoints were improvements in metabolic (including fasting glucose, homeostasis model assessment-estimated insulin resistance (HOMA-IR), hemoglobin A1c (HBA1C), C-peptide, insulin and lipid profiles) and inflammatory (including nuclear factor k-B (NF-KB), tumor necrosis factor (TNF-α), high sensitive- C reactive protein(hs-CRP)) parameters from baseline to the end of treatment.

Results

Neither chlorogenic acid nor caffeine was superior to placebo in attenuation of the hepatic fat and stiffness and other hepatic outcomes in patients with diabetes and NAFLD. Except for the lower level of total cholesterol in caffeine group (p = 0.04), and higher level of insulin in chlorogenic acid plus caffeine group (p = 0.01) compared with placebo, there were no significant differences among the treatment groups.

Conclusion

These findings do not recommend caffeine and/or chlorogenic acid to treat NAFLD in type 2 diabetes patients.

Trial registration

IRCT201707024010N21. Registered 14 September 2017.

A Review of Liver Fibrosis and Emerging Therapies

With the increasing burden of liver cirrhosis, the most advanced stage of hepatic fibrosis, there is a need to better understand the pathological processes and mechanisms to target specific treatments to reverse or cease fibrosis progression. Antiviral therapy for hepatitis B and C has effectively treated underlying causes of chronic liver disease and has induced fibrosis reversal in some; however, this has not been targeted for the majority of aetiologies for cirrhosis including alcohol or nonalcoholic steatohepatitis. Fibrosis, characterised by the accumulation of extracellular matrix proteins, is caused by chronic injury from toxic, infectious, or metabolic causes. The primary event of fibrogenesis is increased matrix production and scar formation mediated by the hepatic stellate cell, which is the principal cell type involved. Experimental models using rodent and human cell lines of liver injury have assisted in better understanding of fibrogenesis, especially in recognising the role of procoagulant factors. This has led to interventional studies using anticoagulants in animal models with reversal of fibrosis as the primary endpoint. Though these trials have been encouraging, no antifibrotic therapies are currently licenced for human use. This literature review discusses current knowledge in the pathophysiology of hepatic fibrosis, including characteristics of the extracellular matrix, signalling pathways, and hepatic stellate cells. Current types of experimental models used to induce fibrosis, as well as up-to-date anticoagulant therapies and agents targeting the hepatic stellate cell that have been trialled in animal and human studies with antifibrotic properties, are also reviewed.

Coffee consumption and liver-related hospitalizations and deaths in the ARIC study

BACKGROUND/OBJECTIVES

Coffee consumption has been found to be associated with reduced risk of chronic conditions such as liver disease. However, less is known about the association between coffee and liver-related hospitalizations and deaths.

SUBJECTS/METHODS

We conducted a prospective analysis on 14,208 participants aged 45-64 years from the Atherosclerosis Risk in Communities (ARIC) study. Coffee consumption (cups/day) was assessed using food frequency questionnaires at visit 1 (1987-89) and visit 3 (1993-95). Liver-related hospitalizations were defined as a hospitalization with any International Classification of Diseases, Ninth Revision (ICD-9) code related to liver disease identified through cohort surveillance. Liver-related death was defined as any death with a liver disease ICD-9 code listed anywhere on the death certificate form.

RESULTS

There were 833 incident cases of liver-related hospitalizations over a median follow-up of 24 years and 152 liver-related deaths over a median follow-up of 25 years. Participants who were in the highest category of coffee consumption (≥ 3 cups/day) were more likely to be men, whites, current smokers, and current alcohol drinkers. In our fully adjusted model, consuming ≥ 3 cups/day of coffee was significantly associated with a reduced risk of liver-related hospitalizations compared with never drinkers (hazard ratio: 0.79, 95% CI: 0.63-0.99). There were no significant associations between coffee consumption and liver-related deaths after adjusting for covariates.

CONCLUSIONS

Coffee drinkers may be at lower risk for liver-related hospitalizations. This supports current evidence that low and moderate levels of coffee may be protective to the liver.

Coffee Consumption and Prevention of Cirrhosis: In Support of the Caffeine Hypothesis

Coffee is acknowledged as the most widely used drug worldwide. Coffee is also a foodstuff, so its use is often used to satisfy dietary urges. When used as a drug, coffee is normally consumed as a stimulant rather than to treat or prevent particular diseases. Recently, coffee consumption has been inversely related to progression of liver fibrosis to cirrhosis and even hepatocellular carcinoma. Experiments in cellular and animal models have provided biological plausibility for coffee as an antifibrotic agent in the liver. A recent article examined one of the key questions regarding the antifibrotic role of coffee-specifically what is the primary antifibrotic agent in coffee? This article briefly reviews the relevant issues with regard to coffee as an antifibrotic agent for patients with chronic liver disease.

Beverage consumption and paediatric NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in children and adolescents, due to the increased worldwide incidence of obesity among children. It is now clear enough that of diet high in carbohydrates and simple sugars are associated with hepatic steatosis and non-alcoholic steatohepatitis (NASH). Several studies have shown that an increased consumption of simple sugars is also positively associated with overweight and obesity, and related co-morbidities, such as type 2 diabetes, metabolic syndrome and NAFLD. It is difficult to define the role of the various components of soft drinks and energy drinks in the pathogenesis of NAFLD and its progression in NASH, but the major role is played by high calorie and high sugar consumption, mainly fructose. In addition, other components of these beverages (e.g. xanthine) seem to have an important role in the pathogenesis of metabolic disorders, crucial pathways involved in NAFLD/NASH. The drastic reduction in the consumption of energy drinks and soft drinks is an appropriate intervention for the prevention of obesity and NAFLD in young people.

Coffee consumption protects against progression in liver cirrhosis and increases long-term survival after liver transplantation

BACKGROUND

Therapeutic options to treat progression of end-stage liver disease (ESLD) or improve long-term survival after liver transplantation remain scarce. We investigated the impact of coffee consumption under these conditions.

METHODS

We recorded coffee consumption habits of 379 patients with ESLD awaiting liver transplantation and 260 patients after liver transplantation. Survival was analyzed based on coffee intake.

RESULTS

One hundred ninety-five patients with ESLD consumed coffee on a daily basis, while 184 patients did not. Actuarial survival was impaired (P = 0.041) in non-coffee drinkers (40.4 ± 4.3 months, 95% confidence interval [CI]: 32.0-48.9) compared with coffee drinkers (54.9 ± 5.5 months, 95% CI: 44.0-65.7). In subgroup analysis, the survival of patients with alcoholic liver disease (ALD; P = 0.020) and primary sclerosing cholangitis (PSC; P = 0.017) was increased with coffee intake while unaffected in patients with chronic viral hepatitis (P = 0.517) or other liver disease entities (P = 0.652). Multivariate analysis showed that coffee consumption of PSC and ALD patients retained as an independent risk factor (odds ratio [OR]: 1.94; 95% CI: 1.15-3.28; P = 0.013) along with MELD score (OR: 1.13; 95% CI: 1.09-1.17; P = 0.000). Following liver transplantation, long-term survival was longer in coffee drinkers (coffee: 61.8 ± 2.0 months, 95% CI: 57.9-65.8) than non-drinkers (52.3 ± 3.5 months, 95% CI: 45.4-59.3; P = 0.001).

CONCLUSIONS

Coffee consumption delayed disease progression in ALD and PSC patients with ESLD and increased long-term survival after liver transplantation. We conclude that regular coffee intake might be recommended for these patients.

Caffeine reduces hepatic lipid accumulation through regulation of lipogenesis and ER stress in zebrafish larvae

BACKGROUND

Caffeine, the main component of coffee, has showed its protective effect on non-alcoholic fatty liver disease (NAFLD) in many studies. However, the hepatoprotection of caffeine and its mechanisms in zebrafish were unexplored. Thus, this study's intentions are to establish a NAFLD model of zebrafish larvae and to examine the role of caffeine on fatty liver with the model.

RESULTS

Growth and the incidence of fatty liver of zebrafish larvae increased with the increased amount of feeding in a dose-dependent manner. The degree of hepatic steatosis of larvae also gradually aggravated with the increased quantity and duration of feeding. Triglyceride contents of zebrafish fed for 20 days significantly increased in model group (180 mg/d) compared with control group (30 mg/d) (P < 0.001). Significant decreases in body weight and hepatic steatosis rate were observed in 2.5, 5, 8 % caffeine treatment group compared with model group (P < 0.05). Hepatic lipid accumulation was also significantly reduced in caffeine treatment larvae. Moreover, caffeine treatment was associated with upregulation of lipid β-oxidation gene ACO and downregulation of lipogenesis-associated genes (SREBP1, ACC1, CD36 and UCP2), ER stress-associated genes (PERK, IRE1, ATF6 and BIP), the inflammatory cytokine genes (IL-1beta and TNF-alpha) and autophagy associated genes (ATG12 and Beclin-1). Protein expression of CHOP, BIP and IL-1beta remarkably reduced in caffeine treatment group compared with model group.

CONCLUSIONS

We induced hepatoteatosis in zebrafish by overfeeding regimen and demonstrated caffeine have a role in suppression of hepatosteatosis by downregulation of genes associated with lipogenesis, ER stress, inflammatory response and enhancement of lipid oxidation, indicating zebrafish model may be used to identify putative pharmacological targets and to test novel drugs for human NAFLD treatment.

Coffee Consumption Decreases Risks for Hepatic Fibrosis and Cirrhosis: A Meta-Analysis

BACKGROUND AND AIM

Previous studies have demonstrated that coffee consumption may be inversely correlated with hepatic fibrosis and cirrhosis. However, the reported results have been inconsistent. To summarize previous evidences quantitatively, a meta-analysis was performed.

METHODS

The Medline, Web of Science, and Embase databases (from inception to June 2015) were searched to identify relevant trials that evaluated the effects of coffee consumption on hepatic fibrosis or cirrhosis. Odds ratios (ORs) of advanced hepatic fibrosis or cirrhosis for low or moderate, high, and any coffee consumption versus no consumption were pooled. Two cups per day was used as the cut-off level between low or moderate and high consumption.

RESULTS

Sixteen studies were included, involving 3034 coffee consumers and 132076 people who do not consume coffee. The pooled results of the meta-analysis indicated that coffee consumers were less likely to develop cirrhosis compared with those who do not consume coffee, with a summary OR of 0.61 (95%CI: 0.45-0.84). For low or moderate coffee consumption versus no consumption, the pooled OR of hepatic cirrhosis was 0.66 (95%CI: 0.47-0.92). High coffee consumption could also significantly reduce the risk for hepatic cirrhosis when compared with no coffee consumption (OR = 0.53, 95%CI: 0.42-0.68). The effect of coffee consumption on hepatic fibrosis was summarized as well. The pooled OR of advanced hepatic fibrosis for coffee consumption versus no consumption was 0.73 (95%CI: 0.58-0.92). The protective effect of coffee on hepatic fibrosis and cirrhosis was also identified in subgroup meta-analyses of patients with alcoholic liver disease and chronic hepatitis C virus (HCV) infection.

CONCLUSION

Coffee consumption can significantly reduce the risk for hepatic fibrosis and cirrhosis.

Diet and upper gastrointestinal malignancies

Diet is believed to modulate cancer risk and this relationship has been widely studied in the gastrointestinal tract. Observational epidemiologic studies have provided most of the evidence about the effects of diet on cancer risk because clinical trials to determine nutritional exposures are often impossible, impractical, or unaffordable. Although a few foods or nutrients are thought to protect against specific types of cancer, it seems clear that the strength and even direction of dietary associations (increasing or decreasing risk) is organ-site- and even histology-specific, along the gastrointestinal tract. Although some hypotheses are supported by a substantial body of observational data (drinking hot maté [an infusion of the herb Ilex Paraguarensis] contributes to esophageal cancer), there are not much data to support others. We discuss some highly touted hypotheses and draw interim conclusions about what is known and what could be done to improve the level of evidence. The complex nature of diet and its associations can be productively investigated with disease-specific studies. However, public health recommendations for normal-risk individuals regarding diet and gastrointestinal cancer should probably emphasize the importance of eating for overall health rather than eating specific foods to reduce risk for specific cancers.

I drink for my liver, Doc: emerging evidence that coffee prevents cirrhosis

Evidence demonstrating that regular ingestion of coffee has salutary effects on patients with chronic liver disease is accumulating rapidly. Specifically, it appears that coffee ingestion can slow the progression of liver fibrosis, preventing cirrhosis and hepatocellular carcinoma (HCC). This should excite clinicians and scientists alike, since these observations, if true, would create effective, testable hypotheses that should lead to improved understanding on fibrosis pathogenesis and thus may generate novel pharmacologic treatments of patients with chronic liver disease.

This review is designed to examine the relevant clinical and epidemiological data in critical fashion and to examine the putative pharmacological effects of coffee relevant to the pathogenesis of liver fibrosis and cirrhosis. We hope that this will inspire relevant critical analyses, especially among “coffee skeptics”. Of note, one major assumption made by this review is that the bulk of the effects of coffee consumption are mediated by caffeine, rather than by other chemical constituents of coffee. Our rationales for this assumption are threefold: first, caffeine’s effects on adenosinergic signaling provide testable hypotheses; second, although there are  myriad chemical constituents of coffee, they are present in very low concentrations, and perhaps more importantly, vary greatly between coffee products and production methods (it is important to note that we do not dismiss the “botanical” hypothesis here; rather, we do not emphasize it at present due to the limitations of the studies examined); lastly, some (but not all) observational studies have examined both coffee and non-coffee caffeine consumption and found consistent effects, and when examined, no benefit to decaffeinated coffee has been observed. Further, in the interval since we examined this phenomenon last, further evidence has accumulated supporting caffeine as the effector molecule for coffee’s salutary effects.

Inverse associations of total and decaffeinated coffee with liver enzyme levels in National Health and Nutrition Examination Survey 1999-2010

Coffee may have hepatoprotective effects and higher coffee consumption has been associated inversely with levels of liver enzymatic markers. However, it is unclear whether decaffeinated coffee is also associated with liver enzymes. The study population included 27,793 participants, age 20 or older, in the U.S. National Health and Nutrition Examination Survey (1999-2010). Coffee intake was evaluated by 24-hour dietary recall. Serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and gamma-glutamyl transaminase (GGT) were measured. We examined the relationship between coffee intake and enzymatic levels using weighted multiple variable logistic (abnormally elevated levels of enzymes) and linear regression (continuous enzymatic levels). Total coffee consumption was inversely associated with abnormal levels of all four liver enzymes and continuous levels of AST, ALP, and GGT. Compared to those reporting no coffee consumption, participants reporting ≥ 3 cups per day had an odds ratio (OR; 95% confidence interval [CI]) of 0.75 (0.63, 0.89), 0.82 (0.68, 0.98), 0.73 (0.55, 0.95), and 0.69 (0.57, 0.83) for abnormal levels of ALT, AST, ALP, and GGT, respectively. Similar inverse associations were found with decaffeinated coffee intake and abnormal levels of ALT (OR (≥ 2 vs 0 cup/d): 0.62 [0.41, 0.94]), AST (0.74 [0.49, 1.11]), and GGT (0.70 [0.49-1.00]).

CONCLUSION

Higher intakes of coffee, regardless of its caffeine content, were associated with lower levels of liver enzymes.

Ethanol-induced oxidant stress modulates hepatic autophagy and proteasome activity

In this review, we describe research findings on the effects of alcohol exposure on two major catabolic systems in liver cells: the ubiquitin-proteasome system (UPS) and autophagy. These hydrolytic systems are not unique to liver cells; they exist in all eukaryotic tissues and cells. However, because the liver is the principal site of ethanol metabolism, it sustains the greatest damage from heavy drinking. Thus, the focus of this review is to specifically describe how ethanol oxidation modulates the activities of the UPS and autophagy and the mechanisms by which these changes contribute to the pathogenesis of alcohol-induced liver injury. Here, we describe the history and the importance of cellular hydrolytic systems, followed by a description of each catabolic pathway and the differential modulation of each by ethanol exposure. Overall, the evidence for an involvement of these catabolic systems in the pathogenesis of alcoholic liver disease is quite strong. It underscores their importance, not only as effective means of cellular recycling and eventual energy generation, but also as essential components of cellular defense.

Obesity and the liver: nonalcoholic fatty liver disease

The increasing prevalence of nonalcoholic fatty liver disease (NAFLD) parallels the rise of obesity and its complications. NAFLD is a common cause of cirrhosis and a leading indication for liver transplant. Genetic susceptibility, dietary composition, and exercise habits influence the development of NAFLD, and insulin resistance results in widespread metabolic perturbations with a net effect of triglyceride accumulation in the liver. Some patients will develop hepatocyte cellular injury and fibrosis of the liver, which can progress to cirrhosis and require liver transplant. Treatments targeting the pathophysiological mechanisms of NAFLD exist, but carry some potential risk and are not universally effective. Weight loss and lifestyle changes remain the most effective and safest approach, but sustainable change is difficult for most patients to achieve. Future work will continue to focus on developing effective and safe interventions to prevent the development of advanced liver disease, whereas efforts in the public health domain continue to combat obesity.