Diurnal changes in the murine small intestine are disrupted by obesogenic Western Diet feeding and microbial dysbiosis

Intestinal functions demonstrate circadian rhythms thought to be entrained, in part, by an organisms’ intrinsic feeding and fasting periods as well as by the intestinal microbiome. Circadian disruption as a result of ill-timed nutrient exposure and obesogenic feeding poses an increased risk to disease. As such, the aim of this study was to assess the relationships between dietary timing, composition, and the microbiome with regard to rhythmic small intestinal structure and mucosal immunity. Rodent chow (RC)-mice exhibited time-dependent increases in small intestinal weight, villus height, and crypt depth as well as an increased proportion of CD8αα⁺ cells and concomitant decrease in CD8αβ+ cells at the onset of the feeding period (p < 0.05–0.001). Western diet (WD)-animals displayed disrupted time-dependent patterns in intestinal structure and lymphocyte populations (p < 0.05–0.01). Antibiotic-induced microbial depletion abrogated the time- and diet-dependent patterns in both RC- and WD-mice (p < 0.05–0.001). However, although germ-free-mice displayed altered rhythms, fecal microbial transfer from RC-mice was generally unsuccessful in restoring structural and immune changes in these animals. This study shows that adaptive changes in the small intestine at the onset of the feeding and fasting periods are disrupted by WD-feeding, and that these changes are dependent, in part, on the intestinal microbiome.

Circadian GLP-1 Secretion in Mice Is Dependent on the Intestinal Microbiome for Maintenance of Diurnal Metabolic Homeostasis

The incretin glucagon-like peptide 1 (GLP-1) is secreted by the intestinal L cell upon nutrient ingestion. GLP-1 also exhibits a circadian rhythm, with highest release at the onset of the feeding period. Similarly, microbial composition and function exhibit circadian rhythmicity with fasting-feeding. The circadian pattern of GLP-1 release was found to be dependent on the oral route of glucose administration and was necessary for the rhythmic release of insulin and diurnal glycemic control in normal male and female mice. In mice fed a Western (high-fat/high-sucrose) diet for 16 weeks, GLP-1 secretion was markedly increased but arrhythmic over the 24-h day, whereas levels of the other incretin, glucose-dependent insulinotropic polypeptide, were not as profoundly affected. Furthermore, the changes in GLP-1 secretion were shown to be essential for the maintenance of normoglycemia in this obesogenic environment. Analysis of the primary L-cell transcriptome, as well as of the intestinal microbiome, also demonstrated time-of-day- and diet-dependent changes paralleling GLP-1 secretion. Finally, studies in antibiotic-induced microbial depleted and in germ-free mice with and without fecal microbial transfer, provided evidence for a role of the microbiome in diurnal GLP-1 release. In combination, these findings establish a key role for microbiome-dependent circadian GLP-1 secretion in the maintenance of 24-h metabolic homeostasis.

Essential Role of Syntaxin-Binding Protein-1 in the Regulation of Glucagon-Like Peptide-1 Secretion

Circadian secretion of the incretin, glucagon-like peptide-1 (GLP-1), correlates with expression of the core clock gene, Bmal1, in the intestinal L-cell. Several SNARE proteins known to be circadian in pancreatic α- and β-cells are also necessary for GLP-1 secretion. However, the role of the accessory SNARE, Syntaxin binding protein-1 (Stxbp1; also known as Munc18-1) in the L-cell is unknown. The aim of this study was to determine whether Stxbp1 is under circadian regulation in the L-cell and its role in the control of GLP-1 secretion. Stxbp1 was highly-enriched in L-cells, and STXBP1 was expressed in a subpopulation of L-cells in mouse and human intestinal sections. Stxbp1 transcripts and protein displayed circadian patterns in mGLUTag L-cells line, while chromatin-immunoprecipitation revealed increased interaction between BMAL1 and Stxbp1 at the peak time-point of the circadian pattern. STXBP1 recruitment to the cytosol and plasma membrane within 30 minutes of L-cell stimulation was also observed at this time-point. Loss of Stxbp1 in vitro and in vivo led to reduced stimulated GLP-1 secretion at the peak time-point of circadian release, and impaired GLP-1 secretion ex vivo. In conclusion, Stxbp1 is a circadian regulated exocytotic protein in the intestinal L-cell that is an essential regulatory component of GLP-1 secretion.

Site-Specific and Temporal Effects of Apraglutide, a Novel Long-Acting Glucagon-Like Peptide-2 Receptor Agonist, on Intestinal Growth in Mice

Long-acting glucagon-like peptide-2 receptor (GLP-2R) agonists are well-established to increase intestinal growth in rodents and, most notably, humans with short bowel syndrome. Most of the trophic effects of GLP-2R agonists are reported to be mediated through increased growth of the crypt-villus axis, resulting in enhanced mucosal mass and improved intestinal function. The present study examined the effects of apraglutide, a novel GLP-2R agonist, on the growth of the small intestine and colon after 3, 7, and 10 weeks of treatment in male and female mice. Apraglutide (3 mg/kg; three times per week) significantly increased small intestinal weight (P < 0.001) and length (P < 0.001) after 3 weeks of administration, with a further increase in effectiveness after 10 weeks (P < 0.01). Crypt depth and villus height were both markedly increased after 3 weeks of apraglutide administration (P < 0.001) but did not show any further increase with duration of treatment, whereas crypt number and intestinal circumference were increased after 7 and 10 weeks (P < 0.01) but not after 3 weeks of apraglutide treatment. Both the weight and the length of the colon were also enhanced by apraglutide treatment for 3 weeks (P < 0.001), and these effects were maintained but did not improve further with continued apraglutide administration. The results of this study demonstrate that the novel, long-acting GLP-2R agonist, apraglutide, demonstrates an unexpected marked ability to increase intestinal length as well as exert time- and location-dependent specificity in its intestinotrophic actions. SIGNIFICANCE STATEMENT: The novel long-acting glucagon-like peptide 2 receptor agonist, apraglutide, enhances intestinal weight as well as intestinal length in a time- and site-dependent fashion.

Baseline characteristics of the diabetic participants in the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT)

OBJECTIVE

Hypertension (HTN) is a major risk factor for cardiovascular disease (CVD) in the setting of diabetes. There is no consensus on how best to treat hypertension among those with diabetes. Here we describe the characteristics of a cohort of hypertensive adults with diabetes who are part of a large prospective blood pressure study. This study will help clarify the treatment of HTN in the setting of diabetes.

RESEARCH DESIGN AND METHODS

The Antihypertensive and Lipid-Lowering high-risk hypertensive participants, ages > or = 55 years, designed to determine whether the incidence of fatal and nonfatal coronary heart disease (CHD) and combined cardiovascular events (fatal and nonfatal CHD, revascularization surgery, angina pectoris, congestive heart failure, and stroke) differs between diuretic (chlorthalidone) treatment and three alternative antihypertensive therapies: a calcium channel blocker (amlodipine), an ACE inhibitor (lisinopril), and an alpha-adrenergic blocker (doxazosin). The planned follow-up is an average of 6 years, to be completed March 2002.

RESULTS

There are 15,297 diabetic individuals in the ALLHAT study (36.0% of the entire cohort). Of these individuals, 50.2% are male, 39.4% are African-American, and 17.7% are Hispanic. Demographic and laboratory characteristics of the cohort are similar to those of other studies of the U.S. elderly population with HTN. The sample size has 42 and 93% confidence, treatments for the two study outcomes.

CONCLUSIONS

The diabetic cohort in ALLHAT wil be able to provide valuable information about the treatment of hypertension in older diabetic patients at risk for incident CVD.

Severe vs moderate energy restriction with and without exercise in the treatment of obesity: efficiency of weight loss

Thirty obese women were randomly assigned to either 40% [severe energy restriction (SER)] or 70% [moderate energy restriction (MER)] of their maintenance energy requirements and to no exercise, aerobic exercise (walking), or aerobic exercise plus circuit weight training. Body composition by hydrostatic weighing and energy expenditure by indirect calorimetry were measured at 0, 3, and 6 mo. In addition, we developed a deficit-efficiency factor (DEF), calculated as body energy loss/dietary energy deficit, to attempt to quantify the effectiveness of the weight-reduction interventions. Subjects in the SER group lost more weight (mean +/- SE: 15.1 +/- 1.4 vs 10.8 +/- 1.0 kg), fat (11.7 +/- 1.1 vs 8.3 +/- 0.6 kg), and fat-free mass (2.8 +/- 0.3 vs 1.8 +/- 0.3 kg) than the MER group (P < or = 0.05). However, the overall DEF was greatest in the MER group (0.80 +/- 0.07) compared with the SER group (0.52 +/- 0.05; P < or = 0.01). Exercise had no significant effect. This study demonstrates that MER may offer an advantage over SER because it produces a greater energy loss relative to energy deficit.

Efficacy and compliance with cholestyramine bar versus powder in the treatment of hyperlipidemia

PURPOSE

The purpose of the study was to compare the powder and the bar forms of cholestyramine to determine efficacy and patient compliance.

SUBJECTS AND METHODS

A prospective, randomized trial was conducted that included 83 healthy men and women with hyperlipidemia greater than the 90th percentile for low-density lipoprotein (LDL) or total cholesterol. Patients were randomly assigned to receive either cholestyramine powder, two packets (8 g), twice daily, or cholestyramine confectionery bar, in maple or mint flavors, two bars (8 g), twice daily. Fasting serum total cholesterol, LDL cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides were measured at baseline, after 6 to 8 weeks of following the American Heart Association Step I diet alone, and after 8 weeks of taking either the cholestyramine bar or powder.

RESULTS

Total cholesterol decreased significantly (p less than 0.01) by 16% in the bar group and 17% in the powder group. LDL cholesterol decreased by 28% and 29% in the bar and powder groups, respectively (p less than 0.01). There was no significant change in HDL cholesterol. Triglycerides increased in both groups, by 29% in the bar group and by 25% in the powder group. There was no difference between bar and powder in the effect on blood lipids. The majority of the lipid-lowering effect was seen within 14 days. Mean patient endpoint compliance with the therapy was 91.8 +/- 3.6% in the bar group and 94.8 +/- 2.1% in the powder group. There was no difference between groups.

CONCLUSION

The cholestyramine confectionery bar is as effective as cholestyramine powder in the treatment of hyperlipidemia. The majority of the lipid-lowering effect is seen within 14 days of therapy. Although patient compliance is comparable between the two forms, gastrointestinal side effects were slightly greater with the bar form. Therefore, although the bar offers an alternative form of therapy, there appears to be no advantage with regard to patient compliance or palatability.

Blood magnesium and potassium alterations with maximal treadmill exercise testing: effects of beta-adrenergic blockade

To test alterations in plasma potassium and magnesium levels with maximal exercise, 15 sedentary, healthy men (mean age 29 years) participated in a double-blind crossover study for 11 weeks with propranolol, atenolol, and placebo. Maximal exercise tests were done at baseline and after placebo and beta-blockade phases. Blood for analysis was collected via indwelling brachial vein angiocatheters at baseline and during and after testing. Plasma potassium and magnesium levels increased at peak exercise with atenolol, propranolol, and placebo. There was no difference among groups in baseline recovery for magnesium (mean 28 minutes, range 24 to 30 minutes). Potassium levels returned to baseline more rapidly (compared with magnesium) in the placebo and atenolol groups (mean 10 minutes); however, recovery time was prolonged with propranolol (26 minutes) compared with placebo and atenolol (p less than 0.01). In conclusion, plasma magnesium and potassium levels increased significantly with maximal exercise and are unaffected by atenolol or propranolol beta-blockade. Propranolol, however (compared with atenolol and placebo), prolongs the time of return to baseline of plasma potassium after exercise.

Effects of exercise testing, training and beta blockade on serum potassium in normal subjects

To evaluate the effects of exercise testing, training and beta blockade on serum potassium, 40 normal subjects (24 men, 16 women, mean age 33 years) had 4 maximal exercise tests with venipuncture for serum potassium before and less than or equal to 40 seconds after each test. After initial exercise testing, they were randomized to atenolol 50 mg daily, atenolol 100 mg daily, propranolol 80 mg twice daily or placebo. All began a 9-week dynamic exercise program for 8 weeks followed by a 1-week drug-free washout period. Tests were done after weeks 1, 8 and 9. A significant mean increase (p less than 0.05) in serum potassium occurred with maximal exercise in the atenolol 50 mg and propranolol groups after 1 week of treatment (mean +/- standard deviation, 4.78 +/- 0.29 to 5.09 +/- 0.43 mEq/liter and 4.81 +/- 0.55 to 5.30 +/- 0.33 mEq/liter). By week 8 after training, all beta blockade groups showed an increase in postmaximal exercise test serum potassium (atenolol 50 mg, 4.78 +/- 0.29 to 5.11 +/- 0.26 mEq/liter; atenolol 100 mg, 4.95 +/- 0.41 to 5.16 +/- 0.36 mEq/liter; propranolol, 4.81 +/- 0.55 to 5.05 +/- 0.29 mEq/liter). After washout, only the placebo group showed an increase in postmaximal test serum potassium (4.99 +/- 0.46 to 5.35 +/- 0.27 mEq/liter). Data indicate that hyperkalemia with maximal exercise testing increases after training with atenolol and propranolol compared to placebo and that this effect resolves once treatment is discontinued.

Exercise testing and training with beta-adrenergic blockade: role of the drug washout period in "unmasking" a training effect

To determine whether or not a training effect can be achieved with beta-adrenergic blockade and whether there is a difference between selective and nonselective therapy, we recruited 40 healthy subjects (16 women, 24 men) to participate in a 9-week exercise training program. After a baseline exercise treadmill test, subjects were randomized to oral therapy groups of atenolol, 50 mg daily (AT 50), atenolol, 100 mg daily (AT 100), propranolol, 80 mg twice a day (Prop), or placebo. Repeat exercise tests were performed at week 1, week 8, and at week 9, with week 8 to 9 being a 1-week drug-free washout period. At week 8, maximal oxygen consumption (Max VO2), when compared with baseline levels, was increased slightly in AT 50 (4.2%) and Prop (2.4%), decreased in AT 100 (5.3%), and increased significantly in the placebo group (12.7%). After washout, Max VO2 increased significantly compared with baseline in AT 50, AT 100, and Prop (9.8%, 10.8%, and 9.8%, respectively). We conclude that there is no significant difference between selective and nonselective beta-blockade therapy in the development of a training effect. This effect, however, may not become apparent until the drug is withdrawn.

Comparisons of the P greater than V sign on the WISC-R and WAIS-R in delinquent males

Comparisons of the WISC-R and WAIS-R were made in a sample of male delinquents (N = 80) to determine whether they would show differences in the degree to which the P greater than V sign occurred on them. A larger split between mean Verbal and mean Performance IQ was found on the WISC-R than on the WAIS-R. Frequency analyses revealed no differences in the number of persons who showed the P greater than V sign on each test. Age and the P greater than V sign were not related significantly. Results suggest that the WISC-R and WAIS-R may not be equivalent measures of this sign, and caution should be exercised in applying results of research on the WISC and WAIS to the revisions of those tests.