Effects of obesity and caloric intake on biliary lipid metabolism in man

Understanding the gastrointestinal tract in obesity: From gut motility patterns to enzyme secretion

BACKGROUND AND PURPOSE

The pathophysiology of obesity has been the product of extensive research, revealing multiple interconnected mechanisms contributing to body weight regulation. The regulation of energy balance involves an intricate network, including the gut-neuroendocrine interplay. As a consequence, research on the gut-brain-microbiota axis in obesity has grown extensively. The physiology of the gastrointestinal tract, far from being underexplored, has significant implications for the development of specific complications in people living with obesity across the fields of gastroenterology, nutrition, and pharmacology. Clinical research indicates higher fasting bile acids serum levels, and blunted postprandial increases in bilious secretions in people living with obesity. Findings are less straightforward for the impact of obesity on gastric emptying with various studies reporting accelerated, normal, or delayed gastric emptying rates. Conversely, the effect of obesity on gastrointestinal pH, gastrointestinal transit, and gastric and pancreatic enzyme secretion is largely unknown. In this review, we explore the current evidence on the gastrointestinal physiology of obesity.

Impact of obesity on liver function tests: is nonalcoholic fatty liver disease the only player? A review article

Objectives

Obesity and nonalcoholic fatty liver disease (NAFLD) are common worldwide health problems with a strong relationship in between. NAFLD is currently the most common cause of abnormal liver function tests (LFT) because of obesity pandemic. The question is NAFLD the only player of abnormal LFT in obesity?

Methodology

This article reviews the most important topics regarding the derangements of LFT in obesity through a PubMed search strategy for all English-language literature.

Results

The reported abnormal LFT in obesity were increased serum levels of transaminases (alanine aminotransaminase, aspartate aminotransaminase), gamma glutamyl transferase, and alkaline phosphatase and decreased serum levels of bilirubin and albumin. Besides novel potential hepatic markers of NAFLD/NASH such as triglycerides/high-density lipoprotein cholesterol ratio, sex hormone-binding globulin, fibroblast growth factor 21, and markers of hepatocyte apoptosis i.e. cytokeratin 18 and microribonucleic acids (miRNAs). Beyond NAFLD, there are other underlying players for the abnormal LFT in obesity such as oxidative stress, inflammation, and insulin resistance.

Conclusion

Derangements of LFT in obesity are attributed to NAFLD but also to obesity itself and its related oxidative stress, insulin resistance, and chronic inflammatory state. Abnormal LFT predict more than just liver disease.

A biosynthetic pathway for the selective sulfonation of steroidal metabolites by human gut bacteria

Members of the human gut microbiome enzymatically process many bioactive molecules in the gastrointestinal tract. Most gut bacterial modifications characterized so far are hydrolytic or reductive in nature. Here we report that abundant human gut bacteria from the phylum Bacteroidetes perform conjugative modifications by selectively sulfonating steroidal metabolites. While sulfonation is a ubiquitous biochemical modification, this activity has not yet been characterized in gut microbes. Using genetic and biochemical approaches, we identify a widespread biosynthetic gene cluster that encodes both a sulfotransferase (BtSULT, BT0416) and enzymes that synthesize the sulfonate donor adenosine 3'-phosphate-5'-phosphosulfate (PAPS), including an APS kinase (CysC, BT0413) and an ATP sulfurylase (CysD and CysN, BT0414-BT0415). BtSULT selectively sulfonates steroidal metabolites with a flat A/B ring fusion, including cholesterol. Germ-free mice monocolonized with Bacteroides thetaiotaomicron ΔBT0416 exhibited reduced gastrointestinal levels of cholesterol sulfate (Ch-S) compared with wild-type B. thetaiotaomicron-colonized mice. The presence of BtSULT and BtSULT homologues in bacteria inhibited leucocyte migration in vitro and in vivo, and abundances of cluster genes were significantly reduced in patients with inflammatory bowel disease. Together, these data provide a mechanism by which gut bacteria sulfonate steroidal metabolites and suggest that these compounds can modulate immune cell trafficking in the host.

Gallstone Formation Follows a Different Trajectory in Bariatric Patients Compared to Nonbariatric Patients

Since obese patients form cholesterol gallstones very rapidly after bariatric surgery, in patients who did not form gallstones during preceding years, we hypothesized that gallstone formation follows a different trajectory in bariatric patients compared to nonbariatric patients. We therefore analyzed the lipid composition of gallbladder bile derived from 18 bariatric gallstone patients and 17 nonbariatric gallstone patients (median (IQR) age, 46.0 (28.0-54.0) years; 33 (94%) female) during laparoscopic cholecystectomy using an enzymatic and lipidomics approach. We observed a higher concentration of total lipids (9.9 vs. 5.8 g/dL), bile acids (157.7 vs. 81.5 mM), cholesterol (10.6 vs. 5.4 mM), and phospholipids (30.4 vs. 21.8 mM) in bariatric gallstone patients compared to nonbariatric gallstone patients. The cholesterol saturation index did not significantly differ between the two groups. Lipidomics analysis revealed an interesting pattern. Enhanced amounts of a number of lipid species were found in the gallbladder bile of nonbariatric gallstone patients. Most striking was a fivefold higher amount of triglyceride. A concomitant ninefold increase of apolipoprotein B was found, suggesting secretion of triglyceride-rich lipoproteins (TRLs) at the canalicular pole of the hepatocyte in livers from nonbariatric gallstone patients. These findings suggest that gallstone formation follows a different trajectory in bariatric patients compared to nonbariatric patients. Impaired gallbladder emptying might explain the rapid gallstone formation after bariatric surgery, while biliary TRL secretion might contribute to gallstone formation in nonbariatric patients.

Risk Factors for Gallstones and Cholecystectomy: A Large-Scale Population-Based Prospective Cohort Study in Japan

INTRODUCTION

Studies investigating the risk of gallstones in the Japanese population are sparse. To our knowledge, this is the first prospective cohort study assessing risk factors of gallstones in Japan.

METHODS

A nationwide population-based prospective cohort of 112,109 men and women, aged 40-69 years, self-completed questionnaires at baseline regarding exposures to potential risk factors, between 1990 and 1994. The occurrence of gallstones and cholecystectomy for gallstones were ascertained from another questionnaire after 10 years. Odds ratios and the 95% confidence intervals were calculated using the multivariate logistic regression.

RESULTS

During the 10-year follow-up, 3,092 (5.0%) participants developed gallstones and 729 (1.2%) participants required cholecystectomy. Increasing age, high body mass index, and diabetes mellitus were associated with the risk of gallstones in both sexes. In men, weight gain or loss of >5 kg over the follow-up period and stress were associated with risk of gallstones, whereas alcohol intake was inversely associated with the risk. In women, weight gain of >5 kg during the follow-up period, smoking, menopause, and lipid-lowering drugs were associated with risk of gallstones, whereas late onset of menarche was inversely associated with risk of gallstones. The risk of cholecystectomy broadly reflected the risk of gallstones for both sexes respectively.

CONCLUSION

Risk factors for both gallstones and cholecystectomy for gallstones are multifactorial and differ between men and women. Novel findings in this study include an inverse association between late onset of menarche and gallstones, and an association between self-reported stress in men and gallstones.

Observational and Genetic Associations of Body Mass Index and Hepatobiliary Diseases in a Relatively Lean Chinese Population

IMPORTANCE

There is some support for the existence of genetic associations between adiposity and certain hepatobiliary diseases in Western populations. However, there is little evidence of such genetic associations in China, where the causes of these diseases may differ from those in Western populations and the mean body mass index (BMI) is much lower.

OBJECTIVES

To compare the observational associations of BMI with hepatobiliary diseases and liver biomarkers with the genetic associations between BMI and these factors and to assess whether the genetic associations of BMI with liver diseases differed by hepatitis B virus infection status.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study used data from the prospective China Kadoorie Biobank, including 473 938 adults aged 30 to 79 years without hepatobiliary diseases at baseline from 10 diverse areas in China from June 25, 2004, to July 15, 2008. A random sample of 75 736 participants with genotyping data was included in the Mendelian randomization analysis. Follow-up was completed January 1, 2017 (median [interquartile range] length of follow-up, 10.2 [9.2-11.1] years). Data were analyzed from January to October 2019.

EXPOSURES

Measured BMI obtained during the baseline survey and genetically instrumented BMI derived using 92 single-nucleotide variations.

MAIN OUTCOMES AND MEASURES

Incident cases of hepatobiliary diseases, liver enzymes, fatty liver index, and fibrosis score.

RESULTS

Among 473 938 individuals (276 041 [58.2%] women), the mean (SD) age was 52 (10.9) years and mean (SD) BMI was 23.8 (3.4). Baseline BMI was associated with higher risks of chronic liver disease (adjusted risk ratio per 1-SD increase, 1.14; 95% CI, 1.11 to 1.17) and gallbladder disease (adjusted risk ratio per 1-SD increase, 1.29; 95% CI, 1.27 to 1.31), with heterogeneity by disease subtype (P < .001). Genetically instrumented BMI was associated with higher risks of chronic liver disease (risk ratio per 1-SD increase, 1.55; 95% CI, 1.08 to 2.24) and gallbladder disease (risk ratio per 1-SD increase, 1.40; 95% CI, 1.11 to 1.76), with no heterogeneity between subtypes. A meta-analysis of the genetic associations in China Kadoorie Biobank and those calculated in UK Biobank gave a risk ratio of 1.55 (95% CI, 1.30 to 1.84) for chronic liver disease and 1.42 (95% CI, 1.22 to 1.64) for gallbladder disease. In the China Kadoorie Biobank study, there were positive genetic associations of BMI with liver enzymes, steatosis, and fibrosis scores, consistent with observational associations. The genetic associations of BMI with liver diseases and biomarkers did not differ by hepatitis B virus infection status.

CONCLUSIONS AND RELEVANCE

In this cohort study of a relatively lean Chinese population, there were positive genetic associations of BMI with hepatobiliary diseases. These results suggest that maintaining a healthy weight through diet and physical activity may help prevent hepatobiliary diseases.

Targeting bile acid metabolism in obesity reduction: A systematic review and meta-analysis

A systematic review and meta-analysis was conducted of studies that address the association of bile acid (BA) with obesity and of studies on the effects of treatment in patients with obesity on BA metabolism, assessed from systemic BA, fibroblast growth factor 19 (FGF19), 7α-hydroxy-4-cholesten-3-one (C4) level, and faecal BA. We searched PubMed, Embase, and the Cochrane Library from inception to 1 August 2019 using the keywords obesity, obese, body mass index, and overweight with bile acid, FGF19, FXR, and TGR5. Two reviewers independently searched, selected, and assessed the quality of studies. Data were analysed using either fixed or random effect models with inverse variance weighting. Of 3771 articles, 33 papers were relevant for the association of BA with obesity of which 22 were included in the meta-analysis, and 50 papers were relevant for the effect of obesity interventions on BA of which 20 were included in the meta-analysis. Circulating fasting total BA was not associated with obesity. FGF19 was inversely and faecal BA excretion was positively associated with obesity. Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) modulated BA metabolism, ie, increased BA and FGF19. Our results indicate that BA metabolism is altered in obesity. Certain bariatric surgeries including RYGB and SG modulate BA, whether these underlie the beneficial effect of the treatment should be investigated.

Adolescent gallstones-need for early intervention in symptomatic idiopathic gallstones

BACKGROUND AND AIM

Currently, there is a paucity of the literature describing the natural history of cholelithiasis (CL) and choledocholithiasis (CDL) in adolescent children. This study aims to analyse the changing demographics of paediatric and adolescent gallstones.

METHODOLOGY

Retrospective review of all children (Age 0-18 years) presenting with symptomatic gallstones over the last 15 years (2002-2017) at a single tertiary institution. Demographics, diagnostic and therapeutic information were collected, with a 5-year median follow-up. Statistics were accomplished by Chi-squared analysis of trend and Student t test.

RESULTS AND DISCUSSIONS

188 children were seen with symptomatic CL. In the 0-11-year-old group, there were 13 females and 16 males (0.8: female to male ratio). There were 130 females and 29 males in the 12-18-year-old group (4.5:1 female to male ratio). The mean weight at presentation was 81.78 kg and the median age was 16 years. Idiopathic gallstones were found in 131 patients (82%). 137 required cholecystectomy (86%) and ERCP was required in 32 patients (20%). 48 adolescents (30.2%) with gallstones had an associated CDL, compared to six children (20%). All of the adolescent patients with CDL had idiopathic gallstones. Gallstone pancreatitis was noted in eighteen adolescents (11%) and one child (3%). We analysed the ideal time to operate on adolescent patients with symptomatic gallstones using the relationship between the length of delay from initial diagnosis to definitive management of CDL and incidence of complications. The analysis demonstrated that for every 10 days treatment was delayed, the risk of subsequent presentations with a symptomatic episode was increased by 5% (p = 0.0004).

CONCLUSION

The current trend of gallstones in adolescent children seems to be a disease primarily of adolescent girls. Symptomatic idiopathic gallstones in adolescents are associated with high rates of common bile duct obstruction and pancreatitis and consequently warrant an early cholecystectomy for all adolescents.

LEVEL OF EVIDENCE

Level IV Treatment Study.

Pancreatic and mucosal enzymes in choline phospholipid digestion

The digestion of choline phospholipids is important for choline homeostasis, lipid signaling, postprandial lipid and energy metabolism, and interaction with intestinal bacteria. The digestion is mediated by the combined action of pancreatic and mucosal enzymes. In the proximal small intestine, hydrolysis of phosphatidylcholine (PC) to 1-lyso-PC and free fatty acid (FFA) by the pancreatic phospholipase A₂ IB coincides with the digestion of the dietary triacylglycerols by lipases, but part of the PC digestion is extended and must be mediated by other enzymes as the jejunoileal brush-border phospholipase B/lipase and mucosal secreted phospholipase A₂ X. Absorbed 1-lyso-PC is partitioned in the mucosal cells between degradation and reacylation into chyle PC. Reutilization of choline for hepatic bile PC synthesis, and the reacylation of 1-lyso-PC into chylomicron PC by the lyso-PC-acyl-CoA-acyltransferase 3 are important features of choline recycling and postprandial lipid metabolism. The role of mucosal enzymes is emphasized by sphingomyelin (SM) being sequentially hydrolyzed by brush-border alkaline sphingomyelinase (alk-SMase) and neutral ceramidase to sphingosine and FFA, which are well absorbed. Ceramide and sphingosine-1-phosphate are generated and are both metabolic intermediates and important lipid messengers. Alk-SMase has anti-inflammatory effects that counteract gut inflammation and tumorigenesis. These may be mediated by multiple mechanisms including generation of sphingolipid metabolites and suppression of autotaxin induction and lyso-phosphatidic acid formation. Here we summarize current knowledge on the roles of pancreatic and mucosal enzymes in PC and SM digestion, and its implications in intestinal and liver diseases, bacterial choline metabolism in the gut, and cholesterol absorption.

Risk of cholecystectomy in morbidly obese patients after bariatric surgery in Taiwan

PURPOSE

The anatomic rearrangement of the gastrointestinal tract after bariatric surgery may result in alterations in the bile acid pool and consequently, gallstone disease. We aimed to investigate whether patients undergoing bariatric surgery are at risk of developing gallbladder disease postoperatively.

PATIENTS AND METHODS

We conducted a population-based cohort study by using claims data from the Taiwan National Health Insurance Research Database. The study cohort comprised 4197 patients diagnosed with morbid obesity.

RESULTS

Among the morbidly obese patients, 2698 underwent bariatric surgery. Females and younger subjects were more prevalent in the surgical group than non-surgical group. Bariatric surgery reduced all obesity-related comorbidities. Cox proportional hazards regression was performed, which revealed increased risk of cholecystectomy after bariatric surgery among obese patients (adjusted hazard ratio, 3.43; p=0.0165). After adjusting for sex and age, the incidence of cholecystectomy was increased in the females population (adjusted hazard ratio, 3.74; p<0.05) and in 30-64 years-old-group (adjusted hazard ratio: 3.69, p<0.05). The cumulative incidence rate of cholecystectomy showed an increased tendency in those undergoing bariatric surgery by log-rank test.

CONCLUSION

Based on the Taiwan database population-based cohort study, bariatric surgery increases the risk of cholecystectomy among morbidly obese patients, especially in the female population and patients aged 30-64 years.

Gallbladder bile supersaturated with cholesterol in gallstone patients preferentially develops from shortage of bile acids

Gallstone (GS) formation requires that bile is supersaturated with cholesterol, which is estimated by a cholesterol saturation index (CSI) calculated from gallbladder (GB) total lipids and the mol% (mole percent) of bile acids (BAs), cholesterol, and phospholipids (PLs). Whereas CSI indicates GS risk, we hypothesized that additional comparisons of GB lipid mol% data are inappropriate to identify why CSI is increased in GS disease. We anticipated that GB lipid mmol/l (millimole per liter) levels should instead identify that, and therefore retrieved GB mmol/l data for BAs, cholesterol, and PLs from a study on 145 GS and 87 GS-free patients and compared them with the corresponding mol% data. BA and PL mmol/l levels were 33% and 31% lower in GS patients, while cholesterol was unaltered. CSI was higher in GS patients and correlated inversely with GB levels of BAs and PLs, but not with cholesterol. A literature search confirmed, in 13 studies from 11 countries, that GB BA levels and, to a certain extent, PLs are strongly reduced in GS patients, while cholesterol levels are not elevated. Our findings show that a shortage of BAs is a major reason why GB bile is supersaturated with cholesterol in GS patients. These results are sustainable because they are also valid from a global perspective.

Effects of Altering Levothyroxine Dose on Energy Expenditure and Body Composition in Subjects Treated With LT4

Background

It is unclear whether variations in thyroid status within or near the reference range affect energy expenditure, body mass, or body composition.

Methods

138 subjects treated with levothyroxine (LT4) for hypothyroidism with normal TSH levels underwent measurement of total, resting, and physical activity energy expenditure; thermic effect of food; substrate oxidation; dietary intake; and body composition. They were assigned to receive an unchanged, higher, or lower LT4 dose in randomized, double-blind fashion, targeting one of three TSH ranges (0.34 to 2.50, 2.51 to 5.60, or 5.61 to 12.0 mU/L). The doses were adjusted every 6 weeks to achieve target TSH levels. Baseline measures were reassessed at 6 months.

Results

At study end, the mean LT4 doses and TSH levels were 1.50 ± 0.07, 1.32 ± 0.07, and 0.78 ± 0.08 µg/kg (P < 0.001) and 1.85 ± 0.25, 3.93 ± 0.38, and 9.49 ± 0.80 mU/L (P < 0.001), respectively, in the three arms. No substantial metabolic differences in outcome were found among the three arms, although direct correlations were observed between decreases in thyroid status and decreases in resting energy expenditure for all subjects. The subjects could not ascertain how their LT4 dose had been adjusted but the preferred LT4 dose they perceived to be higher (P < 0.001).

Conclusions

Altering LT4 doses in subjects with hypothyroidism to vary TSH levels in and near the reference range did not have major effects on energy expenditure or body composition. Subjects treated with LT4 preferred the perceived higher LT4 doses despite a lack of objective effect. Our data do not support adjusting LT4 doses in patients with hypothyroidism to achieve potential improvements in weight or body composition.

Fast Morphological Gallbladder Changes Triggered by a Hypercholesterolemic Diet

INTRODUCTION AND AIM

Obesity is a worldwide epidemic problem, described as a risk factor for hepatic diseases, such as non-alcoholic fatty liver disease and other pathologies related to development of cholesterol crystals and cholesterol gallbladder stones. It has been reported that cholesterol overload may cause hepatic damage; however, little is known about the effects of an acute hypercholesterolemic diet on the gallbladder. The aim of this manuscript was to evaluate the impact of a cholesterol-rich diet on the gallbladder.

MATERIAL AND METHODS

The study included ten eight-week-old C57BL6 male mice, which were divided into two study groups and fed different diets for 48 h: a hypercholesterolemic diet and a balanced Chow diet. After 48 h, the mice were analyzed by US with a Siemens Acuson Antares equipment. Mice were subsequently sacrificed to carry out a cholesterol analysis with a Refloton System (Roche), a crystal analysis with a Carl Zeiss microscope with polarized light, and a histological analysis with Hematoxylin-eosin staining.

RESULTS

The hypercholesterolemic diet induced an increase in gallbladder size and total cholesterol content in the bile, along with important histological changes.

CONCLUSION

Cholesterol overloads not only trigger hepatic damage, but also affect the gallbladder significantly.

Effects of aqueous extract of Arctium lappa L. roots on serum lipid metabolism

Objective

To identify potential genes that may be involved in lipid metabolism in rats after treatment with aqueous extract of Arctium lappa L (burdock).

Methods

Rats were randomly divided into six groups: (i) control (standard diet); (ii) model group (high-fat diet only); (iii) high-fat diet and low-dose aqueous burdock root extract (2 g/kg); (iv) high-fat diet and moderate-dose aqueous burdock root extract (4 g/kg); (v) high-fat diet and high-dose aqueous burdock root extract (8 g/kg); and (vi) a positive control group exposed to a high-fat diet and simvastatin (10 mg/kg). Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was performed to find the potential candidate genes involved in the modulation of blood lipids by treatment with aqueous burdock root extract.

Results

Burdock root extract reduced body weight and cholesterol levels in rats. KEGG analysis revealed 113 genes that were involved in metabolic pathways. Of these, 27 potential genes associated with blood lipid metabolism were identified.

Conclusions

Aqueous extract of burdock root reduced body weight and cholesterol in rats, possibly by modulating the differential expression of genes.

Thyroid Function Variation in the Normal Range, Energy Expenditure, and Body Composition in L-T4-Treated Subjects

PURPOSE

It is not clear whether upper limits of the thyrotropin (TSH) reference range should be lowered. This debate can be better informed by investigation of whether variations in thyroid function within the reference range have clinical effects. Thyroid hormone plays a critical role in determining energy expenditure, body mass, and body composition, and therefore clinically relevant variations in these parameters may occur across the normal range of thyroid function.

METHODS

This was a cross-sectional study of 140 otherwise healthy hypothyroid subjects receiving chronic replacement therapy with levothyroxine (L-T4) who had TSH levels across the full span of the laboratory reference range (0.34 to 5.6 mU/L). Subjects underwent detailed tests of energy expenditure (total and resting energy expenditure, thermic effect of food, physical activity energy expenditure), substrate oxidation, diet intake, and body composition.

RESULTS

Subjects with low-normal (≤2.5 mU/L) and high-normal (>2.5 mU/L) TSH levels did not differ in any of the outcome measures. However, across the entire group, serum free triiodothyronine (fT3) levels were directly correlated with resting energy expenditure, body mass index (BMI), body fat mass, and visceral fat mass, with clinically relevant variations in these outcomes.

CONCLUSIONS

Variations in thyroid function within the laboratory reference range have clinically relevant correlations with resting energy expenditure, BMI, and body composition in L-T4-treated subjects. However, salutary effects of higher fT3 levels on energy expenditure may be counteracted by deleterious effects on body weight and composition. Further studies are needed before these outcomes should be used as a basis for altering L-T4 doses in L-T4-treated subjects.

Acute caloric restriction counteracts hepatic bile acid and cholesterol deficiency in morbid obesity

BACKGROUND

Bile acid (BA) synthesis is regulated by BA signalling in the liver and by fibroblast growth factor 19 (FGF19), synthesized and released from the intestine. In morbid obesity, faecal excretion and hepatic synthesis of BAs and cholesterol are strongly induced and caloric restriction reduces their faecal excretion considerably. We hypothesized that the high intestinal food mass in morbidly obese subjects promotes faecal excretion of BAs and cholesterol, thereby creating a shortage of both BAs and cholesterol in the liver.

METHODS

Ten morbidly obese women (BMI 42 ± 2.6 kg m^-2 ) were monitored on days 0, 3, 7, 14 and 28 after beginning a low-calorie diet (800-1100 kcal day^-1 ). Serum was collected and liver size and fat content determined. Synthesis of BAs and cholesterol was evaluated from serum markers, and the serum levels of lipoproteins, BAs, proprotein convertase subtilisin/kexin type 9 (PCSK9), insulin, glucose and FGF19 were monitored. Fifty-four nonobese women (BMI <25 kg m^-2 ) served as controls.

RESULTS

At baseline, synthesis of both BAs and cholesterol and serum levels of BAs and PCSK9 were elevated in the obese group compared to controls. Already after 3 days on a low-calorie diet, BA and cholesterol synthesis and serum BA and PCSK9 levels normalized, whereas LDL cholesterol increased. FGF19 and triglyceride levels were unchanged, and liver volume was reduced by 10%.

CONCLUSIONS

The results suggest that hepatic BAs and cholesterol are deficient in morbid obesity. Caloric restriction rapidly counteracts these deficiencies, normalizing BA and cholesterol synthesis and circulating PCSK9 levels, indicating that overproduction of cholesterol in enlarged peripheral tissues cannot explain this phenotype. We propose that excessive food intake promotes faecal loss of BAs and cholesterol contributing to their hepatic deficiencies.

Body Mass Index Can Increase the Risk of Gallbladder Cancer: A Meta-Analysis of 14 Cohort Studies

BACKGROUND This study sought to appraise the association between raised body mass index (BMI) and the risk of gallbladder cancer (GBC) by performing a meta-analysis of 14 cohort studies. MATERIAL AND METHODS Eligible cohort studies were selected by searching PubMed and EMBASE from their inception to May 26, 2016, and the reference lists of retrieved articles were also consulted. The information was screened by two authors separately. We used a fixed-effects model to calculate the overall pooled risk estimates. A random-effects model was used to identify heterogeneity. RESULTS The meta-analysis incorporated 14 cohort studies. Nine papers were deemed to be of high quality based on the Newcastle-Ottawa Scale (NOS). Compared with normal weight (BMI 18.5-24.9 kg/m²), the overall pooled relative risks (RR) of GBC was 1.45 (95% CI 1.30-1.61) for excess body weight individuals (BMI ≥25 kg/m²); 1.10 (95% CI 1.02-1.18) for overweight persons (BMI 25-29.9 kg/m²) and 1.69(95% CI 1.54-1.86) for obese folks (BMI ≥30 kg/m²). A higher risk of GBC was presented in obese women (women: RR 1.78, 95% CI 1.59-1.99; men: RR 1.50, 95% CI 1.25-1.79). And a positive relationship between overweight and GBC risk was also displayed in female (RR 1.25, 95% CI 1.11-1.40), but not in male (RR 1.01, 95% CI 0.93-1.11). The sensitivity analysis indicated stable results, and no publication bias was observed. CONCLUSIONS This meta-analysis of 14 cohort studies demonstrated that raised BMI has a dramatic association with risk of GBC, especially in women. But, no association between overweight and GBC in men was found.

Correlations between metabolic syndrome, serologic factors, and gallstones

[Purpose] This study investigated the serologic factors associated with metabolic syndrome and gallstones. [Subjects and Methods] The study evaluated subjects who visited a health promotion center in Seoul from March 2, 2013 to February 28, 2014, and had undergone abdominal ultrasonography. Height, weight, and blood pressure were measured. Blood sampling was performed for high-density lipoprotein cholesterol, triglyceride, fasting blood glucose, total bilirubin, direct bilirubin, indirect bilirubin, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, uric acid, total cholesterol, low-density lipoprotein cholesterol, thyroid stimulating hormone, and red and white blood cell counts. We conducted logistic regression analysis to assess the risk factors associated with metabolic syndrome. [Results] The risk factors for metabolic syndrome in men, in order of decreasing weight, were red blood cell count, body mass index, maximum size of gallstones, white blood cell count, waist circumference, and uric acid level. The factors in women, in order of decreasing weight, were red blood cell count, presence/absence of gallstones, uric acid level, body mass index, fasting blood glucose, and waist circumference. [Conclusion] Most serum biochemical factors and gallstone occurrence could be used to indicate the presence or absence of metabolic syndrome, independent of gender.

Analytic Reviews : Nonsurgical Alternatives in the Management of Gallstones

Until recently, the only therapeutic option for patients with symptomatic gallstones was surgery. However, sev eral new and innovative nonsurgical approaches are cur rently available, including oral dissolution therapy with the bile salts, ursodeoxycholic and chenodeoxycholic acids, instillation of liquid solvents such as methyl tert- butyl ether directly into the gallbladder or the common bile duct, and extracorporeal shock-wave lithotripsy. We review the role of each of these methods in the management of patients with gallstones as well as the epidemiology, pathogenesis, natural history, and radi ological characteristics of gallstones, all important con siderations when choosing appropriate treatment for the individual patient.

Computational model for monitoring cholesterol metabolism

A non-deterministic finite automaton is designed to observe the cholesterol metabolism with the states of acceptance and rejection. The acceptance state of the automaton depicts the normal level of metabolism and production of good cholesterol as an end product. The rejection state of this machine shows the inhibition of enzymatic activity in cholesterol synthesis and removal of free fatty acids. The deficiency in human cholesterol metabolism pathway results in abnormal accumulation of cholesterol in plasma, arterial tissues leading to diseases such as hypercholesterolemia, atherosclerosis respectively and formation of gallstones. The designed machine can be used to monitor the cholesterol metabolism at molecular level through regulation of enzymes involved in the biosynthesis and metabolism of cholesterol for the treatment of diseases incident due to the respective metabolic disorder. In addition, an algorithm for this machine has been developed to compare the programmed string with the given string. This study demonstrates the construction of a machine that is used for the development of molecular targeted therapy for the disorders in cholesterol metabolism.

Bioactive Egg Components and Inflammation

Inflammation is a normal acute response of the immune system to pathogens and tissue injury. However, chronic inflammation is known to play a significant role in the pathophysiology of numerous chronic diseases, such as cardiovascular disease, type 2 diabetes mellitus, and cancer. Thus, the impact of dietary factors on inflammation may provide key insight into mitigating chronic disease risk. Eggs are recognized as a functional food that contain a variety of bioactive compounds that can influence pro- and anti-inflammatory pathways. Interestingly, the effects of egg consumption on inflammation varies across different populations, including those that are classified as healthy, overweight, metabolic syndrome, and type 2 diabetic. The following review will discuss the pro- and anti-inflammatory properties of egg components, with a focus on egg phospholipids, cholesterol, the carotenoids lutein and zeaxanthin, and bioactive proteins. The effects of egg consumption of inflammation across human populations will additionally be presented. Together, these findings have implications for population-specific dietary recommendations and chronic disease risk.

Body mass index, abdominal fatness and the risk of gallbladder disease

Epidemiological studies have indicated a positive association between adiposity and gallbladder disease risk, however, the shape of the dose-response relationship and differences between overall and abdominal adiposity remains to be clarified. We conducted a systematic review and dose-response meta-analysis of cohort studies of body mass index (BMI), waist circumference and waist-to-hip ratio and risk of gallbladder disease. PubMed and Embase databases were searched up to January 9th 2015. Summary relative risks were calculated using a random effects model. Seventeen prospective studies of BMI and gallbladder disease risk with 55,670 cases among 1,921,103 participants were included. The summary relative risk (RR) for a 5 unit increment in BMI was 1.63 (95 % CI 1.49-1.78, I(2) = 98 %). There was evidence of a nonlinear association overall and among women, p(nonlinearity) < 0.0001, but not among men, p(nonlinearity) = 0.99, with a slight flattening of the curve at very high BMI levels (BMI 40-45), however, the risk of gallbladder disease increased almost twofold even within the "normal" BMI range. The summary RR for a 10 cm increase in waist circumference was 1.46 (95 % CI 1.24-1.72, I(2) = 98 %, n = 5) and for a 0.1 unit increment in waist-to-hip ratio was 1.44 (95 % CI 1.26-1.64, I(2) = 92 %, n = 4). Associations were attenuated, but still significant, when BMI and abdominal adiposity measures were mutually adjusted. Our results confirm a positive association between both general and abdominal fatness and the risk of gallbladder disease. There is an almost twofold increase in the risk even within the "normal" BMI range, suggesting that even moderate increases in BMI may increase risk.

Thyroid-stimulating hormone regulates hepatic bile acid homeostasis via SREBP-2/HNF-4α/CYP7A1 axis

BACKGROUND & AIMS

Bile acids (BAs) play a crucial role in dietary fat digestion and in the regulation of lipid, glucose, and energy metabolism. Thyroid-stimulating hormone (TSH) is a hormone produced by the anterior pituitary gland that directly regulates several metabolic pathways. However, the impact of TSH on BA homeostasis remains largely unknown.

METHODS

We analyzed serum BA and TSH levels in healthy volunteers under strict control of caloric intake. Thyroidectomized rats were administered thyroxine and injected with different doses of TSH. Tshr(-/-) mice were supplemented with thyroxine, and C57BL/6 mice were injected with Tshr-siRNA via the tail vein. The serum BA levels, BA pool size, and fecal BA excretion rate were measured. The regulation of SREBP-2, HNF-4α, and CYP7A1 by TSH were analyzed using luciferase reporter, RNAi, EMSA, and CHIP assays.

RESULTS

A negative correlation was observed between the serum levels of TSH and the serum BA levels in healthy volunteers. TSH administration led to a decrease in BA content and CYP7A1 activity in thyroidectomized rats supplemented with thyroxine. When Tshr was silenced in mice, the BA pool size, fecal BA excretion rate, and serum BA levels all increased. Additionally, we found that HNF-4α acts as a critical molecule through which TSH represses CYP7A1 activity. We further confirmed that the accumulation of mature SREBP-2 protein could impair the capacity of nuclear HNF-4α to bind to the CYP7A1 promoter, a mechanism that appears to mediate the effects of TSH.

CONCLUSIONS

TSH represses hepatic BA synthesis via a SREBP-2/HNF-4α/CYP7A1 signaling pathway. This finding strongly supports the notion that TSH is an important pathophysiological regulator of liver BA homeostasis independently of thyroid hormones.

Bile acid signaling through farnesoid X and TGR5 receptors in hepatobiliary and intestinal diseases

BACKGROUND

The well-known functions of bile acids (BAs) are the emulsification and absorption of lipophilic xenobiotics. However, the emerging evidences in the past decade showed that BAs act as signaling molecules that not only autoregulate their own metabolism and enterohepatic recirculation, but also as important regulators of integrative metabolism by activating nuclear and membrane-bound G protein-coupled receptors. The present review was to get insight into the role of maintenance of BA homeostasis and BA signaling pathways in development and management of hepatobiliary and intestinal diseases.

DATA SOURCES

Detailed and comprehensive search of PubMed and Scopus databases was carried out for original and review articles.

RESULTS

Disturbances in BA homeostasis contribute to the development of several hepatobiliary and intestinal disorders, such as non-alcoholic fatty liver disease, liver cirrhosis, cholesterol gallstone disease, intestinal diseases and both hepatocellular and colorectal carcinoma.

CONCLUSION

Further efforts made in order to advance the understanding of sophisticated BA signaling network may be promising in developing novel therapeutic strategies related not only to hepatobiliary and gastrointestinal but also systemic diseases.

Upregulation of hepatic bile acid synthesis via fibroblast growth factor 19 is defective in gallstone disease but functional in overweight individuals

BACKGROUND

Fibroblast growth factor 19 (FGF19) is an enteric hormone regulating bile acid de novo synthesis by sensing ileal bile acid flux. However, the role of FGF19 in cholelithiasis has not yet been elucidated and therefore is investigated in the present study.

METHODS

Total mRNA and protein were isolated from ileal biopsies and used for tissue expression analysis. FGF19, 7α-hydroxycholesterol (7α-OH-Chol), 27-hydroxycholesterol (27-OH-Chol), and different bile acids were determined in the blood samples.

RESULTS

FGF19 serum levels did not differ between gallstone carriers and controls but were significantly decreased in the overweight individuals (-32%, p = 0.0002), irrespective of gallstone status (normalweight to overweight controls -29%, p = 0.0017; normalweight to overweight gallstone carriers -44%, p = 0.0338), and correlated inversely with bodyweight (p < 0.0001, ρ = -0.3317). Compared to non-overweight controls, apical sodium-dependent bile acid transporter expression was significantly diminished in the non-overweight gallstone carriers (-42%, P mRNA = 0.0393; -52%, p protein = 0.0169) as well as in the overweight controls (-24%, P mRNA = 0.0148; -43%, p protein = 0.0017). FGF19 expression varied widely and was similar in all groups. A significant negative correlation was noted between 7α-OH-Chol, 27-OH-Chol, and FGF19 serum levels (p < 0.01; ρ7α-OH-Chol = -0.2155; ρ27-OH-Chol = -0.2144) in obesity.

CONCLUSION

Upregulation of hepatic bile acid synthesis via FGF 19 is defective in gallstone disease but functional in overweight individuals.

Determinants of second-order bile duct visualization at CT cholangiography in potential living liver donors

OBJECTIVE

The purpose of this article is to investigate the determinants of second-order bile duct visualization at CT cholangiography in living potential liver donors.

MATERIALS AND METHODS

We retrospectively identified 143 potential living liver donors (83 men and 60 women; mean age, 37 years) evaluated with CT cholangiography, which included a slow infusion of iodipamide meglumine with CT acquisition 15 minutes after biliary contrast agent administration. Two readers independently scored the visualization of the second-order bile duct branches on a previously established 4-point scale (0 = not seen, 1 = faintly seen, 2 = well seen, and 3 = excellent visualization). Multivariate analysis was used to investigate the correlation between visualization scores and potential determinants of second-order bile duct opacification, specifically age, body mass index, creatinine level, total and direct bilirubin levels, alkaline phosphatase level, aspartate aminotransferase level, alanine aminotransferase level, patient maximum linear width, CT noise, and hepatosplenic attenuation difference at unenhanced CT.

RESULTS

The mean (± SD) second-order bile duct visualization scores were 2.35 ± 0.66 and 2.55 ± 0.60 for readers 1 and 2, respectively. In the multivariate analysis, the only independent predictors of reduced second-order bile duct visualization were higher alkaline phosphatase level (p = 0.01) and higher CT noise (p = 0.02).

CONCLUSION

Higher serum alkaline phosphatase level and higher CT noise in potential living liver donors indicate a higher risk of poor second-order bile duct visualization at CT cholangiography.

Gallstone-related complications after Roux-en-Y gastric bypass: a prospective study

BACKGROUND

Gastric bypass is a widespread bariatric procedure that carries a high incidence of gallstone formation postoperatively. Controversy exists regarding the importance and consequences of gallstones in these patients. There are surgeons who consider gallstone-related complications after gastric bypass important enough to require routine removal of the gallbladder during gastric bypass (prophylactic cholecystectomy). However, this can lead to increased costs and risks. This study aimed to identify complications related to cholelithiasis after Roux-en-Y gastric bypass (RYGBP).

METHODS

This is a prospective observational study of 40 morbidly obese patients free of gallbladder disease. The patients underwent open RYGBP at a public hospital in Brazil from February to October 2007. They were followed up clinically and ultrasonographically at 6 months and 1, 2, and 3 years after surgery. Of the patients, 38 patients were followed up for 3 years.

RESULTS

Eleven patients (28.9%) developed cholelithiasis, four (10.5%) experienced biliary pain, and 2 suffered from acute biliary pancreatitis (5.3%). These patients had their gallbladders removed laparoscopically. No patient presented with acute cholecystitis, choledocholithiasis, or bile duct dilation during the follow-up period. There were no deaths.

CONCLUSIONS

Gallstone-related complications after RYGBP were relatively common. Some of these complications, like acute pancreatitis, are known to have potentially severe outcomes. It seems reasonable to perform cholecystectomy during gastric bypass in the presence of cholelithiasis or after this procedure if gallstones develop.

Balancing cholesterol synthesis and absorption in the gastrointestinal tract

Cholesterol balance is achieved both by synthesis in the body and by absorption in the gastrointestinal tract. Cholesterol synthesis and absorption are also critical determinants of plasma LDL cholesterol concentrations. In clinical practice, inhibitors of synthesis and inhibitors of absorption are both effective methods of lowering LDL cholesterol concentrations and may be utilized in combination. This review rationalizes these mechanisms of LDL reductions by placing them in the context of cholesterol balance as it is determined by digestive lipid metabolism.

A physiologically based in silico kinetic model predicting plasma cholesterol concentrations in humans

Increased plasma cholesterol concentration is associated with increased risk of cardiovascular disease. This study describes the development, validation, and analysis of a physiologically based kinetic (PBK) model for the prediction of plasma cholesterol concentrations in humans. This model was directly adapted from a PBK model for mice by incorporation of the reaction catalyzed by cholesterol ester transfer protein and contained 21 biochemical reactions and eight different cholesterol pools. The model was calibrated using published data for humans and validated by comparing model predictions on plasma cholesterol levels of subjects with 10 different genetic mutations (including familial hypercholesterolemia and Smith-Lemli-Opitz syndrome) with experimental data. Average model predictions on total cholesterol were accurate within 36% of the experimental data, which was within the experimental margin. Sensitivity analysis of the model indicated that the HDL cholesterol (HDL-C) concentration was mainly dependent on hepatic transport of cholesterol to HDL, cholesterol ester transfer from HDL to non-HDL, and hepatic uptake of cholesterol from non-HDL-C. Thus, the presented PBK model is a valid tool to predict the effect of genetic mutations on cholesterol concentrations, opening the way for future studies on the effect of different drugs on cholesterol levels in various subpopulations in silico.

Gallstone disease in children

Gallstone disease in children is evolving, and for the previous 3 decades, the frequency for surgery has increased greatly. This is in part because of improved diagnostic modalities, but also changing pathology, an increased awareness of emerging comorbidities, such as childhood obesity, and other associated risk factors. This article outlines the pathophysiology, genetics, and predisposing factors for developing gallstones and includes a review of the literature on the current and more novel medical and surgical techniques to treat this interesting disease.

[Obesity and gallbladder diseases]

Obesity is an important health problem in the world and related to many critical diseases, such as diabetes, cardiovascular disease, and metabolic syndrome. Obesity leads to fat infiltration of multiple organs and infiltrated adipose tissue produces many cytokines resulting in the dysfunction of organs such as the gallbladder. In the biliary diseases, obesity and overweight have been known as a major risk factor for gallstones. According to current studies, obesity, insulin resistance, hyperinsulinemia, and metabolic syndrome are related to various gallbladder diseases including gallbladder stones, cholecystitis, gallbladder polyps, and gallbladder cancers. We reviewed further literature on the obesity and gallbladder diseases, in aspects of epidemiology, mechanism, pathology and prevention.

The use of stable and radioactive sterol tracers as a tool to investigate cholesterol degradation to bile acids in humans in vivo

Alterations of cholesterol homeostasis represent important risk factors for atherosclerosis and cardiovascular disease. Different clinical-experimental approaches have been devised to study the metabolism of cholesterol and particularly the synthesis of bile acids, its main catabolic products. Most evidence in humans has derived from studies utilizing the administration of labeled sterols; these have several advantages over in vitro assay of enzyme activity and expression, requiring an invasive procedure such as a liver biopsy, or the determination of fecal sterols, which is cumbersome and not commonly available. Pioneering evidence with administration of radioactive sterol derivatives has allowed to characterize the alterations of cholesterol metabolism and degradation in different situations, including spontaneous disease conditions, aging, and drug treatment. Along with the classical isotope dilution methodology, other approaches were proposed, among which isotope release following radioactive substrate administration. More recently, stable isotope studies have allowed to overcome radioactivity exposure. Isotope enrichment studies during tracer infusion has allowed to characterize changes in the degradation of cholesterol via the "classical" and the "alternative" pathways of bile acid synthesis. Evidence brought by tracer studies in vivo, summarized here, provides an exceptional tool for the investigation of sterol metabolism, and integrate the studies in vitro on human tissue.

Clinical characteristics and risk factors for symptomatic pediatric gallbladder disease

OBJECTIVE

Our center previously reported its experience with pediatric gallbladder disease and cholecystectomies from 1980 to 1996. We aimed to determine the current clinical characteristics and risk factors for symptomatic pediatric gallbladder disease and cholecystectomies and compare these findings with our historical series.

STUDY DESIGN

Retrospective, cross-sectional study of children, 0 to 18 years of age, who underwent a cholecystectomy from January 2005 to October 2008.

RESULTS

We evaluated 404 patients: 73% girls; 39% Hispanic and 35% white. The mean age was 13.10 ± 0.91 years. The primary indications for surgery in patients 3 years or older were symptomatic cholelithiasis (53%), obstructive disease (28%), and biliary dyskinesia (16%). The median BMI percentile was 89%; 39% were classified as obese. Of the patients with nonhemolytic gallstone disease, 35% were obese and 18% were severely obese; BMI percentile was 99% or higher. Gallstone disease was associated with hemolytic disease in 23% (73/324) of patients and with obesity in 39% (126/324). Logistic regression demonstrated older age (P = .019) and Hispanic ethnicity (P < .0001) as independent risk factors for nonhemolytic gallstone disease. Compared with our historical series, children undergoing cholecystectomy are more likely to be Hispanic (P = .003) and severely obese (P < .0279).

CONCLUSION

Obesity and Hispanic ethnicity are strongly correlated with symptomatic pediatric gallbladder disease. In comparison with our historical series, hemolytic disease is no longer the predominant risk factor for symptomatic gallstone disease in children.

The aetiology of symptomatic gallstones quantification of the effects of obesity, alcohol and serum lipids on risk. Epidemiological and biomarker data from a UK prospective cohort study (EPIC-Norfolk)

OBJECTIVE

The development of gallstones is influenced by obesity and alcohol. This study aimed to precisely quantify these risks and investigate whether the aetiological mechanism may involve serum lipids, for the first time using a European prospective cohort study.

METHODS

The European Prospective Investigation into Cancer-Norfolk, recruited 25 639 men and women, aged 40 to 74 years, between 1993 and 1997. At enrolment weight, height and alcohol intake were recorded and nonfasting blood samples taken to measure serum triglycerides, cholesterol, high-density lipoproteins and low-density lipoproteins. The cohort was monitored for 14 years for symptomatic gallstones. Cox regression estimated sex-specific hazard ratios (HRs) for symptomatic gallstones adjusted for covariates.

RESULTS

Symptomatic gallstones developed in 296 people (67.9% women). For each additional unit of BMI, the HR in men was 1.08 [95% confidence interval (CI)=1.02-1.14]; in women the HR was 1.08 (95% CI=1.06-1.11). Every unit of alcohol consumed per week decreased risk in men by 3% (HR=0.97, 95% CI=0.95-0.99) with no effect in women. Serum triglycerides increased risk in men (highest vs. lowest quarter HR=2.02, 95% CI=1.03-3.98) and women (HR=2.43, 95% CI=1.52-3.90). Increased high-density lipoprotein was associated with a decreased risk in men (highest vs. lowest quarter HR=0.22, 95% CI=0.09-0.52) and women (HR=0.55, 95% CI=0.36-0.85). No effects were found for serum cholesterol and low-density lipoprotein.

CONCLUSION

Obesity and alcohol influence gallstone formation, possibly in part through their effects on serum lipids. Reducing obesity may prevent gallstones in the population, as 38% of incident cases of gallstones were associated with a BMI of more than 25.

Dissecting the role of insulin resistance in the metabolic syndrome

PURPOSE OF REVIEW

Over 20 years ago, insulin resistance was postulated to play a central role in the pathogenesis of the metabolic syndrome. However, this has been difficult to prove, leading to a great deal of controversy within the field. Recent studies on mice and humans with genetic defects in insulin signaling have allowed us, for the first time, to dissect which features of the metabolic syndrome can be caused by insulin resistance.

RECENT FINDINGS

Liver insulin receptor knockout mice show that hepatic insulin resistance can produce hyperglycemia, increased apolipoprotein B secretion and atherosclerosis, and increased biliary cholesterol secretion and cholesterol gallstones. Many of these changes may be due to disinhibition of the transcription factor, forkhead box O1. Yet, neither liver insulin receptor knockout mice nor humans with insulin receptor mutations develop the hypertriglyceridemia or hepatic steatosis associated with the metabolic syndrome.

SUMMARY

These data point to a central role for insulin resistance in the pathogenesis of the metabolic syndrome, as hyperglycemia, atherosclerosis, and cholesterol gallstones can all be caused by insulin resistance. However, hypertriglyceridemia and hepatic steatosis are not due directly to insulin resistance and should be considered pathogenically distinct features of the metabolic syndrome.

Hepatic insulin resistance directly promotes formation of cholesterol gallstones

Despite the well-documented association between gallstones and the metabolic syndrome, the mechanistic links between these two disorders remain unknown. Here we show that mice solely with hepatic insulin resistance, created by liver-specific disruption of the insulin receptor (LIRKO mice) are markedly predisposed toward cholesterol gallstone formation due to at least two distinct mechanisms. Disinhibition of the forkhead transcription factor FoxO1, increases expression of the biliary cholesterol transporters Abcg5 and Abcg8, resulting in an increase in biliary cholesterol secretion. Hepatic insulin resistance also decreases expression of the bile acid synthetic enzymes, particularly Cyp7b1, and produces partial resistance to the farnesoid X receptor, leading to a lithogenic bile salt profile. As a result, after twelve weeks on a lithogenic diet, all of the LIRKO mice develop gallstones. Thus, hepatic insulin resistance provides a crucial link between the metabolic syndrome and increased cholesterol gallstone susceptibility.

The response of lipoproteins to dietary fat and cholesterol in lean and obese persons

Individuals differ in the response of their blood lipoproteins to cholesterol-lowering diets. One characteristic clearly associated with susceptibility to diet is leanness; many studies show that total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol concentrations respond more strongly to dietary fat and cholesterol in lean subjects than in obese subjects. This is unlikely to be due to differences in dietary compliance. A metabolic explanation is that obese people have a higher rate of total body cholesterol synthesis. The low-density lipoprotein receptors in their liver cells are partly suppressed by this large stream of endogenous cholesterol coming in from their enterohepatic circulation, and the amount added by dietary cholesterol relative to the endogenous pool would be less than in lean people. Whatever the mechanism, diets low in saturated fat and cholesterol are less effective in the obese. The most effective way for obese people to normalize their blood lipids is to lose weight, which is, unfortunately, hard to do in our society.

Low serum levels of ghrelin are associated with gallstone disease

AIM: To explore the role of ghrelin in gallstone disease.

METHODS: We carried out a cross-sectional study in 150 subjects, 38 with gallstones (cases) and 112 controls. We also did a real-time PCR-RT study in twenty gallbladder samples each. Body mass index (BMI), serum insulin, ghrelin, and serum lipids were measured. Logistic regression analyses (univariate and multivariate) were conducted to estimate the probability of gallstone disease associated with serum ghrelin concentrations.

RESULTS: Cases were statistically different from controls in gender distribution (P = 0.01), age (53 vs 44 yr, P = 0.002), BMI (28 vs 25; P = 0.004), and glucose (5.26 vs 4.98 mmol/L; P = 0.05). The prevalence of ghrelin serum levels above the third tercile was lower in subjects without metabolic syndrome (P < 0.05). In a multivariate model, we found a protective effect, when ghrelin values were higher than the median value (OR = 0.27, 95%CI 0.09-0.82, P = 0.02). Twenty (20%) gallbladder specimens expressed ghrelin mRNA.

CONCLUSION: Serum ghrelin concentrations are associated with a protective effect of GD.

The response of lipoproteins to dietary fat and cholesterol in lean and obese persons

Individuals differ in the response of their blood lipoproteins to cholesterol-lowering diets. One characteristic clearly associated with susceptibility to diet is leanness; many studies show that total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol concentrations respond more strongly to dietary fat and cholesterol in lean subjects than in obese subjects. This is unlikely to be due to differences in dietary compliance. A metabolic explanation is that obese people have a higher rate of total body cholesterol synthesis. The low-density lipoprotein receptors in their liver cells are partly suppressed by this large stream of endogenous cholesterol coming in from their enterohepatic circulation, and the amount added by dietary cholesterol relative to the endogenous pool would be less than in lean people. Whatever the mechanism, diets low in saturated fat and cholesterol are less effective in the obese. The most effective way for obese people to normalize their blood lipids is to lose weight, which is, unfortunately, hard to do in our society.