Inhibition of isoproterenol-induced lipolysis in rat inguinal adipocytes in vitro by physiological melatonin via a receptor-mediated mechanism.

Because the pineal hormone melatonin has been implicated in affecting adiposity in rats and fatty acid transport in certain rat tumor models, we tested whether melatonin regulates lipolysis in a normal cell system in vitro. Adipocytes were isolated from the inguinal fat pads (i.e. sc fat) of Sprague Dawley male rats during mid-light phase. Lipolysis was stimulated with isoproterenol (3 microM), and cells were incubated for 4 h in the presence or absence of a physiological circulating concentration of melatonin (1 nM). Lipolysis was measured by determining the amount of glycerol present in the incubation buffer, expressed as nmol glycerol/mg cellular fatty acid. We observed a 20- to 30-fold stimulation of basal lipolysis by isoproterenol, and this stimulation was inhibited 50--70% by melatonin. Melatonin exhibited this effect over a wide range of concentrations tested (100 pM-1 microM) with an IC(50) of approximately 500 pM. The effect by melatonin (1 nM) was completely blocked by pertussis toxin (50 ng/ml), by 8-bromo-cAMP (10 nM), and by the melatonin receptor antagonist S-20928 (1 nM). These results suggest that the antilipolytic effect occurs through one of the G(i) protein-coupled melatonin receptors because we have shown that both the mt(1) (Mel 1a) and MT(2) (Mel 1b) melatonin receptors are expressed in inguinal adipocytes. Melatonin inhibition of lipolysis was not observed in adipocytes isolated from rat epididymal fat pads (i.e. visceral fat), even though these cells also express both the mt(1) and MT(2) receptors. The results indicate that physiological circulating concentrations of melatonin inhibit isoproterenol-induced lipolysis in rat adipocytes via a G protein-coupled melatonin receptor-mediated signal transduction pathway in a site-specific manner.

Biomarkers of human colonic cell growth are influenced differently by a history of colonic neoplasia and the consumption of acarbose.

The nutritional effects of butyrate on the colonic mucosa and studies of transformed cells suggest that butyrate has anti-colon cancer effects. If butyrate has antineoplastic effects, mucosal growth contrasts between normal subjects and those with a history of colonic neoplasia would parallel changes in growth characteristics caused by butyrate in a colon neoplasia population. To test this hypothesis, rectal biopsies from a survey of colonoscopy patients (n = 50) with and without a history of colonic neoplasia (controls) were compared. Similarly, rectal biopsies were compared from subjects (n = 44) with a colon neoplasia history in an acarbose-placebo crossover trial. Control subjects in the colonoscopy survey had higher bromodeoxyuridine (BrdU) uptake than subjects with a history of neoplasia (P = 0.05). The control subjects also had a higher correlation of BrdU and Ki-67 labeling (P = 0.003). Both findings were paralleled by acarbose use. Acarbose augmented BrdU uptake (P = 0.0001) and improved the correlation of BrdU and Ki-67 labeling (P = 0.013). Acarbose also augmented fecal butyrate (P = 0.0001), which was positively correlated with Ki-67 labeling (P = 0.003). p52 antigen had an earlier pattern of crypt distribution in subjects with a history of colon neoplasia but was not affected by acarbose use. Lewis-Y antigen was expressed earlier in the crypt with acarbose but had similar expression in the colonoscopy survey groups. The use of acarbose to enhance fecal butyrate concentration produced mucosal changes paralleling the findings in control subjects as opposed to those with neoplasia, supporting the concept of an antineoplastic role for butyrate.

Dim light during darkness stimulates tumor progression by enhancing tumor fatty acid uptake and metabolism.

Tumor linoleic acid uptake and metabolism, and growth are suppressed by melatonin, the synthesis of which is inhibited by light. Linoleic acid, via its mitogenic metabolite 13-hydroxyoctadecadienoic acid (13-HODE) is an important growth stimulant of rat hepatoma 7288CTC. Here we compared the effects of an alternating light:dark cycle (12L:12D), dim light (0.25 lux) present during the dark phase of a diurnal light cycle, and constant light on growth and fatty acid metabolism in hepatoma 7288CTC. Our results show that dim light suppressed melatonin release by the pineal gland, increased tumor linoleic acid uptake and 13-HODE production, and promoted tumor growth as effectively as did constant light.

Acarbose enhances human colonic butyrate production.

Earlier studies suggest that butyrate has colonic differentiating and nutritional effects and that acarbose increases butyrate production. To determine the effects of acarbose on colonic fermentation, subjects were given 50-200 mg acarbose or placebo (cornstarch), three times per day, with meals in a double-blind crossover study. Fecal concentrations of starch and starch-fermenting bacteria were measured and fecal fermentation products determined after incubation of fecal suspensions with and without added substrate for 6 and 24 h. Substrate additions were cornstarch, cornstarch plus acarbose and potato starch. Dietary starch consumption was similar during acarbose and placebo treatment periods, but fecal starch concentrations were found to be significantly greater with acarbose treatment. Ratios of starch-fermenting to total anaerobic bacteria were also significantly greater with acarbose treatment. Butyrate in feces, measured either as concentration or as percentage of total short-chain fatty acids, was significantly greater with acarbose treatment than with placebo treatment. Butyrate ranged from 22.3 to 27.5 mol/100 mol for the 50-200 mg, three times per day doses of acarbose compared with 18.3-19.3 mol/100 mol for the comparable placebo periods. The propionate in fecal total short-chain fatty acids was significantly less with acarbose treatment (10.7-12.1 mol/100 mol) than with placebo treatment (13.7-14.2 mol/100 mol). Butyrate production was significantly greater in fermentations in samples collected during acarbose treatment, whereas production of acetate and propionate was significantly less. Fermentation decreased when acarbose was added directly to cornstarch fermentations. Acarbose effectively augmented colonic butyrate production by several mechanisms; it reduced starch absorption, expanded concentrations of starch-fermenting and butyrate-producing bacteria and inhibited starch use by acetate- and propionate-producing bacteria.

Dietary guar gum alters colonic microbial fermentation in azoxymethane-treated rats.

To assess the effects of guar gum on colonic microbial fermentation and cancer development, azoxymethane-treated rats were fed a partially hydrolyzed guar or control diet. Anaerobic fecal incubations were conducted at 8-wk intervals, either without added substrate or with cornstarch or hydrolyzed guar as substrates. Short-chain fatty acids in colonic contents and colonic carcinoma areas were measured at 27 wk. Fecal in vitro fermentation rates were higher for guar-fed rats than for control rats [three-way ANOVA (diet, time, in vitro substrates), P = 0.002]. Fecal in vitro butyrate production was greater for guar-fed rats than for control rats after 3-11 weeks of diet treatment (three-way ANOVA, P = 0.027). Butyrate concentrations of colonic contents at 27 wk were higher in guar-fed than in control rats and higher in the cecum than in the post-cecal colon (two-way ANOVA, P = 0.0001). A regression equation predicting colonic carcinoma area (r2 = 0.279) using propionate and butyrate concentrations of the contents of the post-cecal colon showed propionate as a positive predictor (P < 0.001) and butyrate as a negative predictor (P = 0.033). Our results show that patterns of short-chain fatty acid production may affect the results of fiber-carcinogenesis experiments. Dietary addition of hydrolyzed guar is associated with fecal fermentation low in propionate and high in butyrate; short-chain fatty acid concentrations are greater proximally than distally. These results suggest that butyrate protects against colonic neoplasia, whereas propionate enhances it, and demonstrate that colonic microbiota adapt to produce more butyrate if given time and the proper substrate.

A crystal-state, solution and theoretical study of the preferred conformation of linear C alpha, alpha-diphenylglycine derivatives and dipeptides with potential anticonvulsant activity.

Several linear molecules containing the C alpha, alpha-diphenylglycine residue were prepared as potential anticonvulsants. The conformational preferences of the C alpha, alpha-diphenylglycine residue were assessed in these synthetic derivatives and dipeptides by X-ray diffraction, FTIR absorption and 1H NMR techniques, and by conformational energy computations. Five (out of six) derivatives adopt the fully extended C5 conformation in the crystal state. This intramolecularly H-bonded form is largely populated in chloroform solution in all the derivatives investigated. Conformational energy computations in vacuo support the view that the intramolecularly H-bonded C7-ring form is the most stable structure for these compounds. Only one linear derivative exhibits a (modest) anticonvulsant activity.

Linear tripeptide conformation. Crystal structures of Cbz-glycylglycyltyrosine methyl ester and Cbz-glycyl(D,L)tyrosylglycine ethyl ester.

The structures of two tripeptides, Cbz-glycylglycyltyrosine methyl ester (ZGGYOMe) and Cbz-glycyl(D,L)tyrosylglycine ethyl ester (ZGYGOEt) have been determined from single-crystal X-ray diffraction data. Crystals of ZGGYOMe are monoclinic, space group P2(1), with a = 12.427(3), b = 4.999(3), c = 17.401(6) A, beta = 99.98(2) degree and Z = 2. The final R-index is 0.049 for 1698 reflections with I > or = to 2 sigma (I). Crystals of ZGYGOEt are monoclinic, space group P2(1)/n with a = 12.134(8), b = 14.614(3), c = 26.154(9) A, beta = 98.78(4) degrees, Z = 8. The final R-index is 0.067 for 4457 reflections with I > or = to 2 sigma (I). Both peptides adopt highly extended structures; principal torsion angles are omega 0 = 175.0(4) degrees, phi 1 = 69.2(5) degrees, psi 1 = -154.9(4) degrees, omega 1 = -175.8(4) degrees, phi 2 = 165.4(4) degrees, psi 2 = 154.2(3) degrees, omega 2 = 169.6(3) degrees, phi 3 = -94.8(5) degrees, psi 3 = -47.6(5) degrees for ZGGYOMe and, for the two independent molecules of ZGYGOEt, omega 0 = 177.9(4) degrees, 178.9(4) degrees, phi 1 = -172.0(4) degrees, 169.7(4) degrees; psi 1 = 174.4(4) degrees, -162.5(4) degrees; omega 1 = -170.1(4) degrees, 176.7(4) degrees; phi 2 = -130.8(4) degrees, 130.3(5) degrees; psi 2 = 162.8(4) degrees, -163.3(4) degrees; omega 2 = -177.6(4) degrees, 176.2(4) degrees; phi 3 = -169.9(4) degrees, 172.9(4) degrees; psi 3 = -168.2(4) degrees, 160.9(4) degrees. The structures are of interest since the first one adopts a conformation unlike those of related GGX sequences and the latter shows an antiparallel hydrogen-bonding pattern.

Molecular structures of L-Leu-L-Tyr, Gly-D,L-Met.p-toluenesulfonate and L-His-L-Leu.

L-Leu-L-Tyr, (I), C15H22N2O4, M(r) = 294.35, crystallizes from MeOH/5% dimethyl sulfoxide in the orthorhombic space group P2(1)2(1)2(1). a = 5.644 (1), b = 12.094 (3), c = 22.548 (4) A, V = 1539.0 (5) A3, Z = 4, Dx = 1.270 g cm-3, Cu K alpha, lambda = 1.54184 A, mu = 7.228 cm-1, F(000) = 632, T = 173 K, final R (on F) = 0.033 for 1347 observations with I > or = 2 sigma (I). (I) crystallizes as a zwitterion with the N-terminus protonated and the C-terminus ionized. The peptide backbone adopts a distorted trans antiparallel beta pleated-sheet conformation, with principal torsion angles psi 1 = 163.7 (2), omega 1 = 158.7 (2), phi 2 = -110.9 (3) and psi 2 = 141.4 (2)degrees. The leucyl residue is in the g-(tg-) conformation while the tyrosyl residue adopts the g- conformation, with the phenol ring twisted from the low-energy perpendicular position. Gly-D,L-Met.p-toluenesulfonate, (II), C7H15N2O3S+.C7H7O3S-, M(r) = 378.47, crystallizes from MeOH/EtOAc in the orthorhombic space group Pbca. a = 33.642 (4), b = 15.951 (1), c = 6.785 (1) A, V = 3641.0 (4) A3, Z = 8, Dx = 1.381 g cm-3, Cu K alpha, lambda = 1.54184 A, mu = 28.865 cm-1, F(000) = 1600, T = 223 K, final R (on F) = 0.055 for 1669 observations with I > or = 3 sigma (I). Gly-D,L-Met exists as a cation with the N- and C-termini protonated, the p-toluenesulfonate being the counterion.(ABSTRACT TRUNCATED AT 250 WORDS)

Cornstarch fermentation by the colonic microbial community yields more butyrate than does cabbage fiber fermentation; cornstarch fermentation rates correlate negatively with methanogenesis.

Fermentations of cornstarch and a cabbage-fiber preparation by human fecal suspensions were studied. The molar percent of butyrate of total short-chain fatty acid products was significantly higher when cornstarch was the substrate. Higher molar percents of butyrate were also produced from cornstarch as compared with endogenous substrate when rat fecal suspensions were used. A range of cornstarch fermentation rates was found with suspensions from 20 human subjects. Rapid fermentaion was associated with the absence of methane production. Methane-negative rat fecal suspensions also fermented cornstarch more rapidly than did methane-positive suspensions. High butyrate production may be important because butyrate provides energy to colonocytes and it regulates differentiation of cultured cells.

Structure of 8-(2,6-dideoxy-beta-ribo-hexopyranosyl)-5-hydroxy-2-(4- hydroxyphenyl)-7-methoxy-4H-1-benzopyran-4-one sesquihydrate, aciculatin.

C22H22O8.1.5H2O, Mr = 441.4, monoclinic, I2, a = 21.037 (7), b = 7.371 (2), c = 27.512 (4) A, beta = 100.34 (2) degrees, V = 4196.8 (8) A3, Z = 8, Dx = 1.397 g cm-3, lambda (Mo K alpha) = 0.71073 A, mu = 1.029 cm-1, F(000) = 1864, T = 295 K, final R (on F) = 0.058 for 2113 observed reflections with I greater than or equal to 2 sigma (I). Aciculatin crystallizes as a sesquihydrate with two independent molecules per asymmetric unit. The 2,6-dideoxy-beta-ribo-hexopyranosyl ring is linked to C8 of the flavone through a beta-C-glycosidic bond. Intramolecular hydrogen bonding occurs between the hydroxyl and ketonic O atoms of the flavone ring system.

Histidyl conformations and short N-H...N hydrogen bonds: structure of D,L-histidyl-L,D-histidine pentahydrate.

D,L-Histidyl-L,D-histidine pentahydrate, C12H16-N6O3.5H2O, Mr = 382.38, F(000) = 408, crystallizes in the monoclinic space group Pc with the cell dimensions a = 9.971 (2), b = 4.745 (2), c = 19.572 (3) A and beta = 96.08 (1) degree, V = 920.6 A3, Z = 2, D chi = 1.379 g cm-3. mu = 1.083 cm-1, T = 295 K, Mo K alpha, lambda = 0.71073 A. Final R (on F) = 0.040 for 1658 observed reflections with I greater than or equal to 3 sigma (I). This dipeptide crystallizes in a zwitterionic form with protonation of the C-terminal imidazole ring. Both histidine units exist in the g+ or 'closed' conformation with C alpha-C beta torsion angles of 67.2 (3) and 63.6 (3) degrees. Principal torsion angles, omega = 176.8 (2). psi 1 = 161.8 (3) and phi 2 = -152.1 (3) degrees, are indicative of a highly extended trans conformation. Intramolecular hydrogen bonding occurs between the imidazole rings [N2D-H2D1...N1D = 2.724 (4) A]. Intermolecular hydrogen bonding occurs between symmetry-related histidine molecules forming chains along the gamma axis and includes another short [2.764 (4) A] N-H...N interaction. The five water molecules occupy channels between adjacent histidine layers.

Proline conformations in linear peptides. Structure determination of the methyl ester of N-benzyloxycarbonyl-L-prolyl-D-alanine (N-Z-L-Pro-D-Ala-OMe).

N-Z-L-Pro-D-Ala-OMe, C17H22N2O5, Mr = 334.38, crystallizes in the orthorhombic space group P2(1)2(1)2(1), with the cell dimensions a = 5.005 (5), b = 17.690 (9) and c = 18.70 (1) A3, V = 1656.3 A3, Z = 4, Dx = 1.341 g cm-3, Cu K alpha, lambda = 1.54184 A, mu = 7.830 cm-1, F(000) = 712, T = 198 K, final R (on F) = 0.036 for 1575 observed reflections with I greater than or equal to 3 sigma(I). The pyrrolidine ring takes on the C2-C gamma-endo conformation. The urethane bond is in the cis conformation [omega 0 = 6.0 (3) degrees] while the peptide bond is in the trans conformation [omega 1 = 170.8 (2) degrees]; phi 1/psi 1 values are -88.0 (3) degrees and 151.3 (2) degrees. Intermolecular hydrogen bonding occurs between the C-terminus and the symmetry-related amide. Systematic examination of the pyrrolidine ring in linear peptides reveals no correlation exists between the cis-trans orientation of the proline and the conformation of the pyrrolidine ring.

Constancy of glucose and starch fermentations by two different human faecal microbial communities.

The fermentation of glucose and corn starch by faecal suspensions from two subjects was examined over a three and a half year period. The substrate specificity and products of the faecal fermentations of each subject were relatively stable during this period and were significantly different between subjects. The major soluble end products of fermentation of glucose or starch were acetate, propionate, and butyrate. Hydrogen temporarily accumulated and was subsequently used in fermentations by both subjects. Hydrogen was used without methane production in fermentations of subject 1, but was used for methane formation in fermentations of subject 2. Although the rates of glucose fermentation were similar between both subjects; subject 1 produced a significantly greater molar ratio of propionate than did subject 2. The rate of fermentation of starch by faecal suspensions from subject 1 was faster than that of subject 2. The molar ratio of butyrate was greater for starch fermentations by subject 2, while the molar ratio of propionate was greater with subject 1. Significant differences were found between subjects in molar ratios and concentration of acetate and propionate and concentrations of butyrate in faeces.

Short chain fatty acid distributions of enema samples from a sigmoidoscopy population: an association of high acetate and low butyrate ratios with adenomatous polyps and colon cancer.

We investigated the distribution of short chain fatty acids (SCFA) in enema samples taken from subjects before sigmoidoscopy as an indicator of possible microbial community differences between subjects subsequently diagnosed as normal or having colonic disorders. The major SCFA in all groups were acetic, propionic, and butyric acids. A significantly higher ratio of acetate to total SCFA and lower ratio of butyrate to total SCFA was found for polyp-colon cancer subjects than for normal subjects. There were no significant differences in the ratios of acetate, propionate, or butyrate between the diverticulosis or inflammatory bowel groups and the normal group. There were no significant sex differences nor were there correlations with the ratios of acetate, propionate or butyrate and age, subject weight, or dry weights of samples. Significant differences in concentrations of individual acids were found between normal and certain diagnostic groups. The difference in proportions of individual SCFA between groups suggest differences in fermentation patterns of the colonic microflora.

Incidence of methanogenic bacteria in a sigmoidoscopy population: an association of methanogenic bacteria and diverticulosis.

This study determined the incidence and concentration of methane-producing bacteria in tap water enema samples of 130 individuals taken before sigmoidoscopy. The number of subjects classified in five major colonic groups were as follows: normal colon 36, diverticulosis 57, inflammatory bowel disease 11, colon polyps 34, and colon cancer 11. Some patients were placed in more than one category. Ninety four of the subjects or 72% had methanogenic bacteria ranging in concentration from 6 to about 3 X 10(10)/g dry weight of faeces. The predominant methanogen in all groups was Methanobrevibacter smithii. Chi-square analysis showed that the incidence of methanogens in concentrations of 10(7)/g dry weight of faeces or greater in patients with diverticulosis (58%) was significantly greater than in normal patients (25%). High methanogen concentrations are associated with excretion of methane in the breath.