The Controversial Role of Human Gut Lachnospiraceae

The complex polymicrobial composition of human gut microbiota plays a key role in health and disease. Lachnospiraceae belong to the core of gut microbiota, colonizing the intestinal lumen from birth and increasing, in terms of species richness and their relative abundances during the host's life. Although, members of Lachnospiraceae are among the main producers of short-chain fatty acids, different taxa of Lachnospiraceae are also associated with different intra- and extraintestinal diseases. Their impact on the host physiology is often inconsistent across different studies. Here, we discuss changes in Lachnospiraceae abundances according to health and disease. With the aim of harnessing Lachnospiraceae to promote human health, we also analyze how nutrients from the host diet can influence their growth and how their metabolites can, in turn, influence host physiology.

Gut Microbiota and Short Chain Fatty Acids: Implications in Glucose Homeostasis

Gut microbiota encompasses a wide variety of commensal microorganisms consisting of trillions of bacteria, fungi, and viruses. This microbial population coexists in symbiosis with the host, and related metabolites have profound effects on human health. In this respect, gut microbiota plays a pivotal role in the regulation of metabolic, endocrine, and immune functions. Bacterial metabolites include the short chain fatty acids (SCFAs) acetate (C2), propionate (C3), and butyrate (C4), which are the most abundant SCFAs in the human body and the most abundant anions in the colon. SCFAs are made from fermentation of dietary fiber and resistant starch in the gut. They modulate several metabolic pathways and are involved in obesity, insulin resistance, and type 2 diabetes. Thus, diet might influence gut microbiota composition and activity, SCFAs production, and metabolic effects. In this narrative review, we discuss the relevant research focusing on the relationship between gut microbiota, SCFAs, and glucose metabolism.

An update on the pathogenesis of cholesterol gallstone disease

PURPOSE OF REVIEW

Gallstone disease is a major epidemiologic and economic burden worldwide, and the most frequent form is cholesterol gallstone disease.

RECENT FINDINGS

Major pathogenetic factors for cholesterol gallstones include a genetic background, hepatic hypersecretion of cholesterol, and supersaturated bile which give life to precipitating cholesterol crystals that accumulate and grow in a sluggish gallbladder. Additional factors include mucin and inflammatory changes in the gallbladder, slow intestinal motility, increased intestinal absorption of cholesterol, and altered gut microbiota. Mechanisms of disease are linked with insulin resistance, obesity, the metabolic syndrome, and type 2 diabetes. The role of nuclear receptors, signaling pathways, gut microbiota, and epigenome are being actively investigated.

SUMMARY

Ongoing research on cholesterol gallstone disease is intensively investigating several pathogenic mechanisms, associated metabolic disorders, new therapeutic approaches, and novel strategies for primary prevention, including lifestyles.

Intestinal Barrier and Permeability in Health, Obesity and NAFLD

The largest surface of the human body exposed to the external environment is the gut. At this level, the intestinal barrier includes luminal microbes, the mucin layer, gastrointestinal motility and secretion, enterocytes, immune cells, gut vascular barrier, and liver barrier. A healthy intestinal barrier is characterized by the selective permeability of nutrients, metabolites, water, and bacterial products, and processes are governed by cellular, neural, immune, and hormonal factors. Disrupted gut permeability (leaky gut syndrome) can represent a predisposing or aggravating condition in obesity and the metabolically associated liver steatosis (nonalcoholic fatty liver disease, NAFLD). In what follows, we describe the morphological-functional features of the intestinal barrier, the role of major modifiers of the intestinal barrier, and discuss the recent evidence pointing to the key role of intestinal permeability in obesity/NAFLD.

Liver Steatosis, Gut-Liver Axis, Microbiome and Environmental Factors. A Never-Ending Bidirectional Cross-Talk

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing worldwide and parallels comorbidities such as obesity, metabolic syndrome, dyslipidemia, and diabetes. Recent studies describe the presence of NAFLD in non-obese individuals, with mechanisms partially independent from excessive caloric intake. Increasing evidences, in particular, point towards a close interaction between dietary and environmental factors (including food contaminants), gut, blood flow, and liver metabolism, with pathways involving intestinal permeability, the composition of gut microbiota, bacterial products, immunity, local, and systemic inflammation. These factors play a critical role in the maintenance of intestinal, liver, and metabolic homeostasis. An anomalous or imbalanced gut microbial composition may favor an increased intestinal permeability, predisposing to portal translocation of microorganisms, microbial products, and cell wall components. These components form microbial-associated molecular patterns (MAMPs) or pathogen-associated molecular patterns (PAMPs), with potentials to interact in the intestine lamina propria enriched in immune cells, and in the liver at the level of the immune cells, i.e., Kupffer cells and stellate cells. The resulting inflammatory environment ultimately leads to liver fibrosis with potentials to progression towards necrotic and fibrotic changes, cirrhosis. and hepatocellular carcinoma. By contrast, measures able to modulate the composition of gut microbiota and to preserve gut vascular barrier might prevent or reverse NAFLD.

COVID-19 and non-alcoholic fatty liver disease: Two intersecting pandemics

BACKGROUND

Initial evidence from China suggests that most vulnerable subjects to COVID-19 infection suffer from pre-existing illness, including metabolic abnormalities. The pandemic characteristics and high-lethality rate of COVID-19 infection have raised concerns about interactions between virus pathobiology and components of the metabolic syndrome.

METHODS

We harmonized the information from the recent existing literature on COVID-19 acute pandemic and mechanisms of damage in non-alcoholic fatty liver disease (NAFLD), as an example of chronic (non-communicable) metabolic pandemic.

RESULTS

COVID-19-infected patients are more fragile with underlying metabolic illness, including hypertension, cardiovascular disease, type 2 diabetes, chronic lung diseases (e.g. asthma, chronic obstructive pulmonary disease and emphysema) and metabolic syndrome. During metabolic abnormalities, expansion of metabolically active fat ('overfat condition') parallels chronic inflammatory changes, development of insulin resistance and accumulation of fat in configuring NAFLD. The deleterious interplay of inflammatory pathways chronically active in NAFLD and acutely in COVID-19-infected patients, can explain liver damage in a subgroup of patients and might condition a worse outcome in metabolically compromised NAFLD patients. In a subgroup of patients with NAFLD, the underlying liver fibrosis might represent an additional and independent risk factor for severe COVID-19 illness, irrespective of metabolic comorbidities.

CONCLUSIONS

NAFLD can play a role in the outcome of COVID-19 illness due to frequent association with comorbidities. Initial evidences suggest that increased liver fibrosis in NAFLD might affect COVID-19 outcome. In addition, long-term monitoring of post-COVID-19 NAFLD patients is advisable, to document further deterioration of liver damage. Further studies are required in this field.

Biochemical mechanisms in drug-induced liver injury: certainties and doubts

Drug-induced liver injury is a significant and still unresolved clinical problem. Limitations to knowledge about the mechanisms of toxicity render incomplete the detection of hepatotoxic potential during preclinical development. Several xenobiotics are lipophilic substances and their transformation into hydrophilic compounds by the cytochrome P-450 system results in production of toxic metabolites. Aging, preexisting liver disease, enzyme induction or inhibition, genetic variances, local O(2) supply and, above all, the intrinsic molecular properties of the drug may affect this process. Necrotic death follows antioxidant consumption and oxidation of intracellular proteins, which determine increased permeability of mitochondrial membranes, loss of potential, decreased ATP synthesis, inhibition of Ca(2+)-dependent ATPase, reduced capability to sequester Ca(2+) within mitochondria, and membrane bleb formation. Conversely, activation of nucleases and energetic participation of mitochondria are the main intracellular mechanisms that lead to apoptosis. Non-parenchymal hepatic cells are inducers of hepatocellular injury and targets for damage. Activation of the immune system promotes idiosyncratic reactions that result in hepatic necrosis or cholestasis, in which different HLA genotypes might play a major role. This review focuses on current knowledge of the mechanisms of drug-induced liver injury and recent advances on newly discovered mechanisms of liver damage. Future perspectives including new frontiers for research are discussed.

Nonalcoholic Fatty Liver Disease (NAFLD). Mitochondria as Players and Targets of Therapies?

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and represents the hepatic expression of several metabolic abnormalities of high epidemiologic relevance. Fat accumulation in the hepatocytes results in cellular fragility and risk of progression toward necroinflammation, i.e., nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Several pathways contribute to fat accumulation and damage in the liver and can also involve the mitochondria, whose functional integrity is essential to maintain liver bioenergetics. In NAFLD/NASH, both structural and functional mitochondrial abnormalities occur and can involve mitochondrial electron transport chain, decreased mitochondrial β-oxidation of free fatty acids, excessive generation of reactive oxygen species, and lipid peroxidation. NASH is a major target of therapy, but there is no established single or combined treatment so far. Notably, translational and clinical studies point to mitochondria as future therapeutic targets in NAFLD since the prevention of mitochondrial damage could improve liver bioenergetics.

The Role of Diet in the Pathogenesis of Cholesterol Gallstones

Cholesterol gallstone disease is a major health problem in Westernized countries and depends on a complex interplay between genetic factors, lifestyle and diet, acting on specific pathogenic mechanisms. Overweigh, obesity, dyslipidemia, insulin resistance and altered cholesterol homeostasis have been linked to increased gallstone occurrence, and several studies point to a number of specific nutrients as risk- or protective factors with respect to gallstone formation in humans. There is a rising interest in the identification of common and modifiable dietetic factors that put the patients at risk of gallstones or that are able to prevent gallstone formation and growth. In particular, dietary models characterized by increased energy intake with highly refined sugars and sweet foods, high fructose intake, low fiber contents, high fat, consumption of fast food and low vitamin C intake increase the risk of gallstone formation. On the other hand, high intake of monounsaturated fats and fiber, olive oil and fish (ω-3 fatty acids) consumption, vegetable protein intake, fruit, coffee, moderate alcohol consumption and vitamin C supplementation exert a protective role. The effect of some confounding factors (e.g., physical activity) cannot be ruled out, but general recommendations about the multiple beneficial effects of diet on cholesterol gallstones must be kept in mind, in particular in groups at high risk of gallstone formation.

Effects of Bifidobacterium longum and Lactobacillus rhamnosus on Gut Microbiota in Patients with Lactose Intolerance and Persisting Functional Gastrointestinal Symptoms: A Randomised, Double-Blind, Cross-Over Study

Functional gastrointestinal symptoms are frequent, and may be driven by several pathogenic mechanisms. Symptoms may persist in lactose intolerant (LI) patients (i.e., subjects with intestinal lactase deficiency, lactose malabsorption producing symptoms), after a lactose-free diet. Our hypothesis was that probiotic and vitamin B6 treatment may be useful to alleviate symptoms in LI patients through a positive modulation of gut microbial composition and relative metabolism. We aimed to test the efficacy of a novel formulation of Bifidobacterium longum BB536 and Lactobacillus rhamnosus HN001 plus vitamin B6 (ZR) in 23 LI subjects with persistent symptoms during a lactose-free diet. Symptoms, microbiome, and metabolome were measured at baseline and after 30 days in a crossover, randomized, double-blind study of ZR versus placebo (PL). Compared with PL, the administration of probiotics and vitamin B6 significantly decreased bloating (p = 0.028) and ameliorated constipation (p = 0.045). Fecal microbiome differed between ZR and PL. ZR drove the enrichment of several genera involved in lactose digestion including Bifidobacerium. Moreover, the relative abundance of acetic acid, 2-methyl-propanoic acid, nonenal, and indolizine 3-methyl increased, while phenol decreased. Our findings highlight the importance of selected probiotics and vitamin B6 to alleviate symptoms and gut dysbiosis in lactose intolerant patients with persistent functional gastrointestinal symptoms.

Hepatic consequences of COVID-19 infection. Lapping or biting?

The outbreak of coronavirus disease 2019 (COVID-19) starting last December in China placed emphasis on liver involvement during infection. This review discusses the underlying mechanisms linking COVID-19 to liver dysfunction, according to recent available information, while waiting further studies. The manifestations of liver damage are usually mild (moderately elevated serum aspartate aminotransferase activities), and generally asymptomatic. Few patients can still develop severe liver problems, and therapeutic options can be limited. Liver dysfunction may affect about one-third of the patients, with prevalence greater in men than women, and in elderly. Mechanisms of damage are complex and include direct cholangiocyte damage and other coexisting conditions such as the use of antiviral drugs, systemic inflammatory response, respiratory distress syndrome-induced hypoxia, sepsis, and multiple organ dysfunction. During new COVID-19 infections, liver injury may be observed. If liver involvement appears during COVID-19 infection, however, attention is required. This is particularly true if patients are older or have a pre-existing history of liver diseases. During COVID-19 infection, the onset of liver damage impairs the prognosis, and hospital stay is longer.

Sourdough Fermented Breads are More Digestible than Those Started with Baker's Yeast Alone: An In Vivo Challenge Dissecting Distinct Gastrointestinal Responses

As a staple food, bread digestibility deserves a marked nutritional interest. Combining wide-spectrum characterization of breads, in vitro nutritional indices, and in vivo postprandial markers of gastrointestinal function, we aimed at comparing the digestibility of sourdough and baker's yeast breads. Microbiological and biochemical data showed the representativeness of the baker´s yeast bread (BYB) and the two sourdough breads (SB and t-SB, mainly differing for the time of fermentation) manufactured at semi-industrial level. All in vitro nutritional indices had the highest scores for sourdough breads. Thirty-six healthy volunteers underwent an in vivo challenge in response to bread ingestion, while monitoring gallbladder, stomach, and oro-cecal motility. SB, made with moderate sourdough acidification, stimulated more appetite and induced lower satiety. t-SB, having the most intense acidic taste, induced the highest fullness perception in the shortest time. Gallbladder response did not differ among breads, while gastric emptying was faster with sourdough breads. Oro-cecal transit was prolonged for BYB and faster for sourdough breads, especially when made with traditional and long-time fermentation (t-SB), whose transit lasted ca. 20 min less than BYB. Differences in carbohydrate digestibility and absorption determined different post-prandial glycaemia responses. Sourdough breads had the lowest values. After ingesting sourdough breads, which had a concentration of total free amino acids markedly higher than that of BYB, the levels in blood plasma were maintained at constantly high levels for extended time.

Cholecystectomy and risk of metabolic syndrome

The gallbladder physiologically concentrates and stores bile during fasting and provides rhythmic bile secretion both during fasting and in the postprandial phase to solubilize dietary lipids and fat-soluble vitamins. Bile acids (BAs), major lipid components of bile, play a key role as signaling molecules in modulating gene expression related to cholesterol, BA, glucose and energy metabolism. Cholecystectomy is the most commonly performed surgical procedure worldwide in patients who develop symptoms and/or complications of cholelithiasis of any type. Cholecystectomy per se, however, might cause abnormal metabolic consequences, i.e., alterations in glucose, insulin (and insulin-resistance), lipid and lipoprotein levels, liver steatosis and the metabolic syndrome. Mechanisms are likely mediated by the abnormal transintestinal flow of BAs, producing metabolic signaling that acts without gallbladder rhythmic function and involves the BAs/farnesoid X receptor (FXR) and the BA/G protein-coupled BA receptor 1 (GPBAR-1) axes in the liver, intestine, brown adipose tissue and muscle. Alterations of intestinal microbiota leading to distorted homeostatic processes are also possible. According to this view, cholecystectomy, via BA-induced changes in the enterohepatic circulation, is a risk factor for the metabolic abnormalities and becomes another “fellow traveler” with, or another risk factor for the metabolic syndrome.

Exercising the hepatobiliary-gut axis. The impact of physical activity performance

BACKGROUND

Physical inactivity puts the populations at risk of several health problems, while regular physical activity brings beneficial effects on cardiovascular disease, mortality and other health outcomes, including obesity, glycaemic control and insulin resistance. The hepatobiliary tract is greatly involved in several metabolic aspects which include digestion and absorption of nutrients in concert with intestinal motility, bile acid secretion and flow across the enterohepatic circulation and intestinal microbiota. Several metabolic abnormalities, including nonalcoholic fatty liver as well as cholesterol cholelithiasis, represent two conditions explained by changes of the aforementioned pathways.

MATERIALS AND METHODS

This review defines different training modalities and discusses the effects of physical activity in two metabolic disorders, that is nonalcoholic fatty liver disease (NAFLD) and cholelithiasis. Emphasis is given to pathogenic mechanisms involving intestinal bile acids, microbiota and inflammatory status.

RESULTS

A full definition of physical activity includes the knowledge of aerobic and endurance exercise, metabolic equivalent tasks, duration, frequency and intensity, beneficial and harmful effects. Physical activity influences the hepatobiliary-gut axis at different levels and brings benefits to fat distribution, liver fat and gallbladder disease while interacting with bile acids as signalling molecules, intestinal microbiota and inflammatory changes in the body.

CONCLUSIONS

Several beneficial effects of physical activity are anticipated on metabolic disorders linking liver steatosis, gallstone disease, gut motility, enterohepatic circulation of signalling bile acids in relation to intestinal microbiota and inflammatory changes.

Targets for current pharmacologic therapy in cholesterol gallstone disease

Gallstone disease is a frequent condition throughout the world and, cholesterol stones are the most frequent form in Western countries. The standard treatment of symptomatic gallstone subjects is laparoscopic cholecystectomy. The selection of patients amenable for nonsurgical, medical therapy is of key importance; a careful analysis should consider the natural history of the disease and the overall costs of therapy. Only patients with mild symptoms and small, uncalcified cholesterol gallstones in a functioning gallbladder with a patent cystic duct are considered for oral litholysis by hydrophilic ursodeoxycholic acid, in the hope of achieving cholesterol desaturation of bile and progressive stone dissolution. Recent studies have raised the possibility that cholesterol-lowering agents that inhibit hepatic cholesterol synthesis (statins) or intestinal cholesterol absorption (ezetimibe), or drugs acting on specific nuclear receptors involved in cholesterol and bile acid homeostasis, may offer, alone or in combination, additional medical therapeutic tools for treating cholesterol gallstones. Recent perspectives on medical treatment of cholesterol gallstone disease are discussed in this article.

A silybin-phospholipids complex counteracts rat fatty liver degeneration and mitochondrial oxidative changes

AIM

To investigate the effectiveness of antioxidant compounds in modulating mitochondrial oxidative alterations and lipids accumulation in fatty hepatocytes.

METHODS

Silybin-phospholipid complex containing vitamin E (Realsil(®)) was daily administered by gavage (one pouch diluted in 3 mL of water and containing 15 mg vitamin E and 47 mg silybin complexed with phospholipids) to rats fed a choline-deprived (CD) or a high fat diet [20% fat, containing 71% total calories as fat, 11% as carbohydrate, and 18% as protein, high fat diet (HFD)] for 30 d and 60 d, respectively. The control group was fed a normal semi-purified diet containing adequate levels of choline (35% total calories as fat, 47% as carbohydrate, and 18% as protein). Circulating and hepatic redox active and nitrogen regulating molecules (thioredoxin, glutathione, glutathione peroxidase), NO metabolites (nitrosothiols, nitrotyrosine), lipid peroxides [malondialdehyde-thiobarbituric (MDA-TBA)], and pro-inflammatory keratins (K-18) were measured on days 0, 7, 14, 30, and 60. Mitochondrial respiratory chain proteins and the extent of hepatic fatty infiltration were evaluated.

RESULTS

Both diet regimens produced liver steatosis (50% and 25% of liver slices with CD and HFD, respectively) with no signs of necro-inflammation: fat infiltration ranged from large droplets at day 14 to disseminated and confluent vacuoles resulting in microvesicular steatosis at day 30 (CD) and day 60 (HFD). In plasma, thioredoxin and nitrosothiols were not significantly changed, while MDA-TBA, nitrotyrosine (from 6 ± 1 nmol/L to 14 ± 3 nmol/L day 30 CD, P < 0.001, and 12 ± 2 nmol/L day 60 HFD, P < 0.001), and K-18 (from 198 ± 20 to 289 ± 21 U/L day 30 CD, P < 0.001, and 242 ± 23 U/L day 60 HFD, P < 0.001) levels increased significantly with ongoing steatosis. In the liver, glutathione was decreased (from 34.0 ± 1.3 to 25.3 ± 1.2 nmol/mg prot day 30 CD, P < 0.001, and 22.4 ± 2.4 nmol/mg prot day 60 HFD, P < 0.001), while thioredoxin and glutathione peroxidase were initially increased and then decreased. Nitrosothiols were constantly increased. MDA-TBA levels were five-fold increased from 9.1 ± 1.2 nmol/g to 75.6 ± 5.4 nmol/g on day 30, P < 0.001 (CD) and doubled with HFD on day 60. Realsil administration significantly lowered the extent of fat infiltration, maintained liver glutathione levels during the first half period, and halved its decrease during the second half. Also, Realsil modulated thioredoxin changes and the production of NO derivatives and significantly lowered MDA-TBA levels both in liver (from 73.6 ± 5.4 to 57.2 ± 6.3 nmol/g day 30 CD, P < 0.01 and from 27.3 ± 2.1 nmol/g to 20.5 ± 2.2 nmol/g day 60 HFD, P < 0.01) and in plasma. Changes in mitochondrial respiratory complexes were also attenuated by Realsil in HFD rats with a major protective effect on Complex II subunit CII-30.

CONCLUSION

Realsil administration effectively contrasts hepatocyte fat deposition, NO derivatives formation, and mitochondrial alterations, allowing the liver to maintain a better glutathione and thioredoxin antioxidant activity.

Chocolate, "Food of the Gods": History, Science, and Human Health

Chocolate is well known for its fine flavor, and its history began in ancient times, when the Maya considered chocolate (a cocoa drink prepared with hot water) the "Food of the Gods". The food industry produces many different types of chocolate: in recent years, dark chocolate, in particular, has gained great popularity. Interest in chocolate has grown, owing to its physiological and potential health effects, such as regulation of blood pressure, insulin levels, vascular functions, oxidation processes, prebiotic effects, glucose homeostasis, and lipid metabolism. However, further translational and epidemiologic studies are needed to confirm available results and to evaluate other possible effects related to the consumption of cocoa and chocolate, verifying in humans the effects hitherto demonstrated only in vitro, and suggesting how best to consume (in terms of dose, mode, and time) chocolate in the daily diet.

Gastrointestinal symptoms and motility disorders in patients with systemic scleroderma

BACKGROUND

Studies on gastrointestinal symptoms, dysfunctions, and neurological disorders in systemic scleroderma are lacking so far.

METHODS

Thirty-eight scleroderma patients (34 limited, 4 diffuse), 60 healthy controls and 68 dyspeptic controls were scored for upper and lower gastrointestinal symptoms (dyspepsia, bowel habits), gastric and gallbladder emptying to liquid meal (functional ultrasonography) and small bowel transit (H2-breath test). Autonomic nerve function was assessed by cardiovascular tests.

RESULTS

The score for dyspepsia (mainly gastric fullness) was greater in scleroderma patients than healthy controls, but lower than dyspeptic controls who had multiple symptoms, instead. Scleroderma patients with dyspepsia had a longer disease duration. Fasting antral area and postprandial antral dilatation were smaller in scleroderma patients than dyspeptic and healthy controls. Gastric emptying was delayed in both scleroderma patients (particularly in those with abnormal dyspeptic score) and dyspeptic controls, who also showed a larger residual area. Despite gallbladder fasting and postprandial volumes were comparable across the three groups, gallbladder refilling appeared delayed in dyspeptic controls and mainly dependent on delayed gastric emptying in scleroderma. Small intestinal transit was also delayed in 74% of scleroderma and 66% of dyspeptic controls. Bowel habits were similar among the three groups. Autonomic neuropathy was not associated with dyspepsia, gastric and gallbladder motility and small intestinal transit.

CONCLUSION

In scleroderma patients dyspepsia (mainly gastric fullness), restricted distension of the gastric antrum and diffuse gastrointestinal dysmotility are frequent features. These defects are independent from the occurrence of autonomic neuropathy.

Increased Colonic Permeability and Lifestyles as Contributing Factors to Obesity and Liver Steatosis

Intestinal permeability (IP) is essential in maintaining gut-metabolic functions in health. An unequivocal evaluation of IP, as marker of intestinal barrier integrity, however, is missing in health and in several diseases. We aimed to assess IP in the whole gastrointestinal tract according to body mass index (BMI) and liver steatosis. In 120 patients (61F:59M; mean age 45 ± SEM 1.2 years, range: 18-75), IP was distinctively studied by urine recovery of orally administered sucrose (SO, stomach), lactulose/mannitol ratio (LA/MA, small intestine), and sucralose (SA, colon). By triple quadrupole mass-spectrometry and high-performance liquid chromatography, we measured urinary recovery of saccharide probes. Subjects were stratified according to BMI as normal weight, overweight, and obesity, and answered questionnaires regarding dietary habits and adherence to the Mediterranean Diet. Liver steatosis was assessed by ultrasonography. IP at every gastrointestinal tract was similar in both sexes and decreased with age. Stomach and small intestinal permeability did not differ according to BMI. Colonic permeability increased with BMI, waist, neck, and hip circumferences and was significantly higher in obese than in lean subjects. As determined by logistic regression, the odds ratio (OR) of BMI increment was significantly higher in subjects in the highest tertile of sucralose excretion, also after adjusting for age and consumption of junk food. The presence of liver steatosis was associated with increased colonic permeability. Patients with lower score of adherence to Mediterranean diet had a higher score of 'junk food'. Intestinal permeability tended to increase in subjects with a lower adherence to Mediterranean diet. In conclusion, colonic (but not stomach and small intestinal) permeability seems to be linked to obesity and liver steatosis independently from dietary habits, age, and physical activity. The exact role of these last factors, however, requires specific studies focusing on intestinal permeability. Results should pave the way to both primary prevention measures and new therapeutic strategies in metabolic and liver diseases.

Irritable bowel syndrome and diet

Irritable bowel syndrome (IBS) is a chronic functional disorder of the gastrointestinal tract and is one of the most commonly diagnosed gastrointestinal diseases. The impact of IBS on the general population is large due to its high prevalence, suboptimal medical treatments and significant economic burden. The pathophysiology of IBS is complex and treatments are often symptom-specific. The most common therapeutic approaches for IBS include education and reassurance, lifestyles (especially nutrition-based interventions), peripherally acting medications (which typically target motility), centrally acting medications (which target visceral hypersensitivity and pain) and psychological interventions (which aim to reduce the effects of stress or symptom-specific anxiety). A beneficial dietary approach might include the following measures: a diet low in fermentable oligo-,di- and monosaccharides and polyols (FODMAPs), limitation or exclusion of gas-producing foods and/or lactose and gluten and fiber supplementation in selected cases. New therapeutic agents, namely nutraceutics, are also an interesting option in the management of IBS patients. This paper will focus on available dietary interventions for IBS and will review the evidence for nutrition-based therapies.

Management of liver cirrhosis between primary care and specialists

This article discusses a practical, evidence-based approach to the diagnosis and management of liver cirrhosis by focusing on etiology, severity, presence of complications, and potential home-managed treatments. Relevant literature from 1985 to 2010 (PubMed) was reviewed. The search criteria were peer-reviewed full papers published in English using the following MESH headings alone or in combination: "ascites", "liver fibrosis", "cirrhosis", "chronic hepatitis", "chronic liver disease", "decompensated cirrhosis", "hepatic encephalopathy", "hypertransaminasemia", "liver transplantation" and "portal hypertension". Forty-nine papers were selected based on the highest quality of evidence for each section and type (original, randomized controlled trial, guideline, and review article), with respect to specialist setting (Gastroenterology, Hepatology, and Internal Medicine) and primary care. Liver cirrhosis from any cause represents an emerging health issue due to the increasing prevalence of the disease and its complications worldwide. Primary care physicians play a key role in early identification of risk factors, in the management of patients for improving quality and length of life, and for preventing complications. Specialists, by contrast, should guide specific treatments, especially in the case of complications and for selecting patient candidates for liver transplantation. An integrated approach between specialists and primary care physicians is essential for providing better outcomes and appropriate home care for patients with liver cirrhosis.

Dynamic carbon 13 breath tests for the study of liver function and gastric emptying

In gastroenterological practice, breath tests (BTs) are diagnostic tools used for indirect, non-invasive assessment of several pathophysiological metabolic processes, by monitoring the appearance in breath of a metabolite of a specific substrate. Labelled substrates originally employed radioactive carbon 14 ((14)C) and, more recently, the stable carbon 13 isotope ((13)C) has been introduced to label specific substrates. The ingested (13)C-substrate is metabolized, and exhaled (13)CO2 is measured by mass spectrometry or infrared spectroscopy. Some (13)C-BTs evaluate specific (microsomal, cytosolic, and mitochondrial) hepatic metabolic pathways and can be employed in liver diseases (i.e. simple liver steatosis, non-alcoholic steato-hepatitis, liver fibrosis, cirrhosis, hepatocellular carcinoma, drug and alcohol effects). Another field of clinical application for (13)C-BTs is the assessment of gastric emptying kinetics in response to liquids ((13)C-acetate) or solids ((13)C-octanoic acid in egg yolk or in a pre-packed muffin or the (13)C-Spirulina platensis given with a meal or a biscuit). Studies have shown that (13)C-BTs, used for gastric emptying studies, yield results that are comparable to scintigraphy and can be useful in detecting either delayed- (gastroparesis) or accelerated gastric emptying or changes of gastric kinetics due to pharmacological effects. Thus, (13)C-BTs represent an indirect, cost-effective and easy method of evaluating dynamic liver function and gastric kinetics in health and disease, and several other potential applications are being studied.

Bile Acids and GPBAR-1: Dynamic Interaction Involving Genes, Environment and Gut Microbiome

Bile acids (BA) are amphiphilic molecules synthesized in the liver from cholesterol. BA undergo continuous enterohepatic recycling through intestinal biotransformation by gut microbiome and reabsorption into the portal tract for uptake by hepatocytes. BA are detergent molecules aiding the digestion and absorption of dietary fat and fat-soluble vitamins, but also act as important signaling molecules via the nuclear receptor, farnesoid X receptor (FXR), and the membrane-associated G protein-coupled bile acid receptor 1 (GPBAR-1) in the distal intestine, liver and extra hepatic tissues. The hydrophilic-hydrophobic balance of the BA pool is finely regulated to prevent BA overload and liver injury. By contrast, hydrophilic BA can be hepatoprotective. The ultimate effects of BA-mediated activation of GPBAR-1 is poorly understood, but this receptor may play a role in protecting the remnant liver and in maintaining biliary homeostasis. In addition, GPBAR-1 acts on pathways involved in inflammation, biliary epithelial barrier permeability, BA pool hydrophobicity, and sinusoidal blood flow. Recent evidence suggests that environmental factors influence GPBAR-1 gene expression. Thus, targeting GPBAR-1 might improve liver protection, facilitating beneficial metabolic effects through primary prevention measures. Here, we discuss the complex pathways linked to BA effects, signaling properties of the GPBAR-1, mechanisms of liver damage, gene-environment interactions, and therapeutic aspects.

Metabolic dysfunction-associated gallstone disease: expecting more from critical care manifestations

About 20% of adults worldwide have gallstones which are solid conglomerates in the biliary tree made of cholesterol monohydrate crystals, mucin, calcium bilirubinate, and protein aggregates. About 20% of gallstone patients will definitively develop gallstone disease, a condition which consists of gallstone-related symptoms and/or complications requiring medical therapy, endoscopic procedures, and/or cholecystectomy. Gallstones represent one of the most prevalent digestive disorders in Western countries and patients with gallstone disease are one of the largest categories admitted to European hospitals. About 80% of gallstones in Western countries are made of cholesterol due to disturbed cholesterol homeostasis which involves the liver, the gallbladder and the intestine on a genetic background. The incidence of cholesterol gallstones is dramatically increasing in parallel with the global epidemic of insulin resistance, type 2 diabetes, expansion of visceral adiposity, obesity, and metabolic syndrome. In this context, gallstones can be largely considered a metabolic dysfunction-associated gallstone disease, a condition prone to specific and systemic preventive measures. In this review we discuss the key pathogenic and clinical aspects of gallstones, as the main clinical consequences of metabolic dysfunction-associated disease.

Recent Advances in the Digestive, Metabolic and Therapeutic Effects of Farnesoid X Receptor and Fibroblast Growth Factor 19: From Cholesterol to Bile Acid Signaling

Bile acids (BA) are amphiphilic molecules synthesized in the liver (primary BA) starting from cholesterol. In the small intestine, BA act as strong detergents for emulsification, solubilization and absorption of dietary fat, cholesterol, and lipid-soluble vitamins. Primary BA escaping the active ileal re-absorption undergo the microbiota-dependent biotransformation to secondary BA in the colon, and passive diffusion into the portal vein towards the liver. BA also act as signaling molecules able to play a systemic role in a variety of metabolic functions, mainly through the activation of nuclear and membrane-associated receptors in the intestine, gallbladder, and liver. BA homeostasis is tightly controlled by a complex interplay with the nuclear receptor farnesoid X receptor (FXR), the enterokine hormone fibroblast growth factor 15 (FGF15) or the human ortholog FGF19 (FGF19). Circulating FGF19 to the FGFR4/β-Klotho receptor causes smooth muscle relaxation and refilling of the gallbladder. In the liver the binding activates the FXR-small heterodimer partner (SHP) pathway. This step suppresses the unnecessary BA synthesis and promotes the continuous enterohepatic circulation of BAs. Besides BA homeostasis, the BA-FXR-FGF19 axis governs several metabolic processes, hepatic protein, and glycogen synthesis, without inducing lipogenesis. These pathways can be disrupted in cholestasis, nonalcoholic fatty liver disease, and hepatocellular carcinoma. Thus, targeting FXR activity can represent a novel therapeutic approach for the prevention and the treatment of liver and metabolic diseases.