Effect of bile acid composition and manipulation of enterohepatic circulation on leptin gene regulation

Grape Polyphenols May Prevent High-Fat Diet-Induced Dampening of the Hypothalamic-Pituitary-Adrenal Axis in Male Mice

Context 

Chronic high-fat diet (HFD) consumption causes obesity associated with retention of bile acids (BAs) that suppress important regulatory axes, such as the hypothalamic-pituitary-adrenal axis (HPAA). HFD impairs nutrient sensing and energy balance due to a dampening of the HPAA and reduced production and peripheral metabolism of corticosterone (CORT).

Objective

We assessed whether proanthocyanidin-rich grape polyphenol (GP) extract can prevent HFD-induced energy imbalance and HPAA dysregulation.

Methods

Male C57BL6/J mice were fed HFD or HFD supplemented with 0.5% w/w GPs (HFD-GP) for 17 weeks.

Results

GP supplementation reduced body weight gain and liver fat while increasing circadian rhythms of energy expenditure and HPAA-regulating hormones, CORT, leptin, and PYY. GP-induced improvements were accompanied by reduced mRNA levels of Il6, Il1b, and Tnfa in ileal or hepatic tissues and lower cecal abundance of Firmicutes, including known BA metabolizers. GP-supplemented mice had lower concentrations of circulating BAs, including hydrophobic and HPAA-inhibiting BAs, but higher cecal levels of taurine-conjugated BAs antagonistic to farnesoid X receptor (FXR). Compared with HFD-fed mice, GP-supplemented mice had increased mRNA levels of hepatic Cyp7a1 and Cyp27a1, suggesting reduced FXR activation and more BA synthesis. GP-supplemented mice also had reduced hepatic Abcc3 and ileal Ibabp and Ostβ, indicative of less BA transfer into enterocytes and circulation. Relative to HFD-fed mice, CORT and BA metabolizing enzymes (Akr1d1 and Srd5a1) were increased, and Hsd11b1 was decreased in GP supplemented mice.

Conclusion

GPs may attenuate HFD-induced weight gain by improving hormonal control of the HPAA and inducing a BA profile with less cytotoxicity and HPAA inhibition, but greater FXR antagonism.

Resistant starch wheat increases PYY and decreases GIP but has no effect on self-reported perceptions of satiety

Dietary fiber has numerous health benefits, such as increasing satiety, and is regularly included in healthy dietary recommendations. However, different types and sources of fiber vary in their chemical properties and biological effects. This double-blind, randomized, placebo-controlled, crossover study investigated the effects of resistant starch type 2 (RS2) from wheat on self-reported perceptions of satiety and associated gut hormones in 30 healthy adults ages 40-65 years of age. Participants consumed rolls made using either RS2-enriched wheat flour or a wild-type flour for one week before a test day during which they ate a mixed meal containing the same roll type. Both self-reported perceptions of satiety and plasma concentrations of gut hormones were measured following the meal to assess whether the RS2-enriched wheat enhanced satiety and suppressed hunger for a longer period than the control wheat. Exploratory analysis indicated that fasting and peak concentration of peptide YY_3-36 (PYY_3-36; q_fast = 0.02, q_peak = 0.02) increased, while peak concentration and iAUC of glucose-dependent insulinotropic peptide (GIP; q_peak < 0.001, q_iAUC < 0.001) decreased after ingesting RS2-enriched wheat. However, self-reported perceptions of hunger or fullness using visual analog scales (VAS) did not differ following the test meal.

Adiposopathy, diabetes mellitus, and primary prevention of atherosclerotic coronary artery disease: treating "sick fat" through improving fat function with antidiabetes therapies

Both obesity and type 2 diabetes mellitus (DM) are worldwide epidemics, an association that is neither incidental nor coincidental. Adipose tissue is as an active endocrine and immune organ whose dysfunction (adiposopathy or "sick fat") is promoted by excessive caloric balance in genetically and environmentally susceptible patients. The resultant adiposopathic responses directly and indirectly contribute to pathologies leading to hyperglycemia, high blood pressure, and dyslipidemia--all major cardiovascular risk factors--as well as to cardiovascular disease (CVD) itself. Toward the goal of primary prevention of CVD among DM patients, clinical trial outcomes evidence support the use of antihypertensive agents, lipid-altering drugs, and antiplatelet agents. Some of the most proactive measures to reduce the onset of cardiovascular risk factors and potentially prevent the onset of DM are early and aggressive nutritional, physical activity, and lifestyle interventions. Such measures improve the functionality of adipose tissue, reduce adiposopathic responses, and thus improve glycemic, blood pressure, and lipid parameters--all of which would be expected to reduce CVD risk. Finally, if nutritional, physical activity, and lifestyle interventions are not successful, and if DM pharmacologic therapies are indicated, then the choice of anti-DM medications should take into consideration the effects of such agents on adipose tissue function and dysfunction, which in turn, affects major CVD risk factors and CVD.

Sodium taurocholate inhibits intestinal adenoma formation in APCMin/+ mice, potentially through activation of the farnesoid X receptor

In light of clinical and biological evidence that bile constituents exert preventive effects against colorectal cancer, we evaluated the influence of oral bilirubin and sodium taurocholate (NaTC) on intestinal tumor formation in APC(Min/+) mice. Mice received bilirubin and/or bovine serum albumin (BSA) and NaTC in the drinking water for 8 weeks, after which the number, size and location of intestinal adenomas were determined. Tissue specimens were analyzed by light microscopy, TUNEL staining, immunohistochemistry for beta-catenin and Ki-67 and quantitative polymerase chain reaction for farnesoid X receptor (FXR)-dependent gene expression. Colon tumor formation also was assessed in azoxymethane (AOM)-treated hyperbilirubinemic Gunn (j/j) and wild-type (+/+) rats. Compared with untreated APC(Min/+) mice, the mean number of intestinal adenomas was markedly lower in both bilirubin (10.5 +/- 0.9 versus 37.0 +/- 5.2; +/-SEM; P < 0.001) and NaTC plus BSA (14.3 +/- 5.4; P = 0.01)-treated animals. Both treatment groups exhibited reduced levels of cellular proliferation in the ileum (by Ki-67 staining), but no differences in TUNEL staining or the percentage of beta-catenin-positive crypts. Bilirubin feeding reduced intestinal inducible nitric oxide synthase expression, but did not alter adenoma multiplicity in APC(Min/+) mice or in AOM-treated j/j versus +/+ rats. Mice receiving NaTC manifested increased intestinal expression of the FXR-regulated genes, Shp, FGF15 and IBABP, and a concomitant decrease in cyclin D1 message. Administering NaTC to APC(Min/+) mice causes a marked reduction in intestinal adenomas. We postulate that this effect is mediated through activation of FXR, leading to increased Shp expression and consequent downregulation of cyclin D1.

Different tumor necrosis factor-alpha-associated leptin expression in rats with dimethylnitrosamine and bile duct ligation-induced liver cirrhosis

Although serum leptin concentrations are reported by several studies to increase in patients with liver cirrhosis, the mechanisms underpinning this increase remain unclear. Circulating tumor necrosis factor alpha (TNF-alpha) concentrations are also recognized to increase in liver cirrhosis. Furthermore, TNF-alpha administration to rodents results in increased expression and secretion of leptin from adipose tissue in a manner dependent on type 1 TNF-alpha receptor (TNF-RI). The present study was undertaken to examine adipose leptin expression and to explore potential relationships between leptin expression and TNF-alpha in subjects with liver cirrhosis. Liver cirrhosis was induced in male Sprague-Dawley rats by dimethylnitrosamine (DMN) administration or by common bile duct ligation (BDL). Ad libitum and pair-fed animals constituted controls. Serum leptin and TNF-alpha concentrations were determined by immunoassay. Gene expression was determined by the reverse transcription-polymerase chain reaction, and protein levels were measured by Western blotting. Serum leptin values after adjustment of body fat mass in DMN-treated rats were significantly higher than in pair-fed or ad libitum groups. Leptin mRNA and protein levels in epididymal fat in DMN rats increased by 1.8-fold and 2.3-fold, respectively, as compared with ad libitum controls, and by 4-fold and 6-fold, respectively, as compared with the pair-fed group. Epididymal TNF-alpha and membranous TNF-RI (mTNF-RI) concentrations were both 2.3 times higher in DMN rats than in ad libitum controls but did not differ between ad libitum and pair-fed groups. Adipose leptin protein levels correlated directly with TNF-alpha and mTNF-RI concentrations in combined DMN, ad libitum, and pair-fed rats (r=0.64 and r=0.49, respectively; P<.05). In BDL-treated rats, however, serum and adipose leptin concentrations were identical to those in ad libitum controls despite 2.1-fold and 2.4-fold increase in epididymal TNF-alpha and mTNF-RI, respectively. TNF-alpha administration to fasting control animals increased serum and adipose leptin concentrations significantly. The observed TNF-alpha-associated leptin up-regulation in DMN-induced, but not in BDL-induced, cirrhotic rats is consistent with distinctly different roles for TNF-alpha in rats with nonbiliary, as opposed to biliary, cirrhosis.

Plasma leptin and the cholesterol saturation of bile are correlated in obese women after weight loss

Increased cholesterol secretion is a major alteration of biliary function in obese subjects Leptin is a regulator of food intake and is increased in plasma of subjects with low energy expenditure and high adiposity. We investigated the relationship between leptin and the cholesterol saturation of bile in obese women before and after weight reduction by energy restriction (5.02 MJ/d). We studied women (n = 14) with a body mass index (BMI) > or = 30 kg/m(2) who were 35.4 +/- 2.3 y old and who did not have a history of gallstones. They were studied by ultrasound to ensure absence of stones or sludge. BMI, gallbladder bile composition, plasma leptin, serum lipids and lipoproteins cholesterol levels were recorded at baseline and after 6 wk of weight reduction. There were decreases in BMI (33.9 +/- 3.1 to 31.1 +/- 3.6 kg/m(2), P < 0.0001) and leptin levels (16.7 +/- 9.7 to 10.0 +/- 6.7 micro mol/L, P < 0.05) during weight loss. After the experimental period, there were positive correlations between plasma leptin levels and BMI (r = 0.71, P < 0.004); leptin levels and the cholesterol saturation index (CSI) (r = 0.53, P < 0.05); the CSI and LDL cholesterol (r = 0.73, P < 0.003); and negative correlations between leptin levels and HDL cholesterol (r = -0.54, P < 0.05) and LDL cholesterol (r = -0.57, P < 0.03). We have shown relationships among HDL cholesterol, CSI and leptin. This could be useful in understanding the pathophysiology of cholesterol gallstone formation in obese people.

Serum leptin concentrations in patients with short-bowel syndrome

BACKGROUND

Short-bowel syndrome is a state of severe malabsorption resulting from absence or removal of the small bowel for several causes. A number of short-bowel patients develop hyperphagia. Leptin, a protein secreted from adipose tissue, signals the amount of energy stores to the brain.

OBJECTIVE

To study body composition and leptin regulation in short-bowel patients and to determine whether or not leptin concentrations are linked with hyperphagia.

DESIGN

We studied 25 short-bowel patients (remnant bowel less than 150 cm) and 31 controls and 10 oral nutrition. Fifteen patients received total parenteral nutrition and 10 oral nutrition. Anthropometric measurements, body composition (by bioelectrical impedance), and cholesterol, triacylglycerol and leptin concentrations were studied in all subjects.

RESULTS

There were no differences between short-bowel patients and controls in anthropometric variables, body composition, or leptin concentrations. Leptin concentrations were higher in short-bowel women than men (9.21+/-8.54 vs. 3.22+/-1.86 ng/ml, P=0.01). Leptin concentrations correlated positively with age (r=0.4, P=0.045), body mass index (r=0.52, P=0.007), fat mass (r=0.67, P=0.001) and body fat (r=0.68, P=0.0001); there were no correlations with other body composition parameters. We found no correlations between parenteral or oral nutrition and body composition parameters, or between leptin concentrations and the presence of hyperphagia. Logistic regression analysis showed that body fat correctly identified leptin concentrations in 60% of patients.

CONCLUSIONS

Body composition, leptin concentrations and leptin regulation in patients with short-bowel syndrome are similar to those of controls. Leptin concentrations do not correlate with hyperphagia in short bowel-patients.

Leptin and the gastrointestinal tract

The discovery of leptin in 1990 was the culmination of earlier work which recognized that communication between the adipocyte and the hypothalamus was important in maintaining body weight. Leptin, which is a 16 kilodalton protein-encoded by the OB gene, is involved in the regulation of food intake, body composition, and energy expenditure through a central feedback mechanism. Initially thought to be adipocyte-specific, the OB gene, as well as the leptin receptor, have been found in a variety of other tissues. Relevant to this review, the leptin gene and its receptor have been identified in the stomach, intestine, liver, and pancreas. Recent data also suggest that leptin may act locally within the gastrointestinal tract to influence intestinal function. This review emphasizes the concept that leptin may be a new gastrointestinal hormone and the need to expand the focus of leptin research to include all phases of weight maintenance, such as nutrient absorption and utilization, in addition to food intake.