Effects of Dietary Fibre (Pectin) and/or Increased Protein (Casein or Pea) on Satiety, Body Weight, Adiposity and Caecal Fermentation in High Fat Diet-Induced Obese Rats.

Dietary constituents that suppress appetite, such as dietary fibre and protein, may aid weight loss in obesity. The soluble fermentable dietary fibre pectin promotes satiety and decreases adiposity in diet-induced obese rats but effects of increased protein are unknown. Adult diet-induced obese rats reared on high fat diet (45% energy from fat) were given experimental diets ad libitum for 4 weeks (n = 8/group): high fat control, high fat with high protein (40% energy) as casein or pea protein, or these diets with added 10% w/w pectin. Dietary pectin, but not high protein, decreased food intake by 23% and induced 23% body fat loss, leading to 12% lower final body weight and 44% lower total body fat mass than controls. Plasma concentrations of satiety hormones PYY and total GLP-1 were increased by dietary pectin (168% and 151%, respectively) but not by high protein. Plasma leptin was decreased by 62% on pectin diets and 38% on high pea (but not casein) protein, while plasma insulin was decreased by 44% on pectin, 38% on high pea and 18% on high casein protein diets. Caecal weight and short-chain fatty acid concentrations in the caecum were increased in pectin-fed and high pea protein groups: caecal succinate was increased by pectin (900%), acetate and propionate by pectin (123% and 118%, respectively) and pea protein (147% and 144%, respectively), and butyrate only by pea protein (309%). Caecal branched-chain fatty acid concentrations were decreased by pectin (down 78%) but increased by pea protein (164%). Therefore, the soluble fermentable fibre pectin appeared more effective than high protein for increasing satiety and decreasing caloric intake and adiposity while on high fat diet, and produced a fermentation environment more likely to promote hindgut health. Altogether these data indicate that high fibre may be better than high protein for weight (fat) loss in obesity.

A neuroendocrine role for chemerin in hypothalamic remodelling and photoperiodic control of energy balance.

Long-term and reversible changes in body weight are typical of seasonal animals. Thyroid hormone (TH) and retinoic acid (RA) within the tanycytes and ependymal cells of the hypothalamus have been implicated in the photoperiodic response. We investigated signalling downstream of RA and how this links to the control of body weight and food intake in photoperiodic F344 rats. Chemerin, an inflammatory chemokine, with a known role in energy metabolism, was identified as a target of RA. Gene expression of chemerin (Rarres2) and its receptors were localised within the tanycytes and ependymal cells, with higher expression under long (LD) versus short (SD) photoperiod, pointing to a physiological role. The SD to LD transition (increased food intake) was mimicked by 2 weeks of ICV infusion of chemerin into rats. Chemerin also increased expression of the cytoskeletal protein vimentin, implicating hypothalamic remodelling in this response. By contrast, acute ICV bolus injection of chemerin on a 12 h:12 h photoperiod inhibited food intake and decreased body weight with associated changes in hypothalamic neuropeptides involved in growth and feeding after 24 hr. We describe the hypothalamic ventricular zone as a key site of neuroendocrine regulation, where the inflammatory signal, chemerin, links TH and RA signaling to hypothalamic remodeling.

Soluble Fermentable Dietary Fibre (Pectin) Decreases Caloric Intake, Adiposity and Lipidaemia in High-Fat Diet-Induced Obese Rats.

Consumption of a high fat diet promotes obesity and poor metabolic health, both of which may be improved by decreasing caloric intake. Satiety-inducing ingredients such as dietary fibre may be beneficial and this study investigates in diet-induced obese (DIO) rats the effects of high or low fat diet with or without soluble fermentable fibre (pectin). In two independently replicated experiments, young adult male DIO rats that had been reared on high fat diet (HF; 45% energy from fat) were given HF, low fat diet (LF; 10% energy from fat), HF with 10% w/w pectin (HF+P), or LF with 10% w/w pectin (LF+P) ad libitum for 4 weeks (n = 8/group/experiment). Food intake, body weight, body composition (by magnetic resonance imaging), plasma hormones, and plasma and liver lipid concentrations were measured. Caloric intake and body weight gain were greatest in HF, lower in LF and HF+P, and lowest in the LF+P group. Body fat mass increased in HF, was maintained in LF, but decreased significantly in LF+P and HF+P groups. Final plasma leptin, insulin, total cholesterol and triglycerides were lower, and plasma satiety hormone PYY concentrations were higher, in LF+P and HF+P than in LF and HF groups, respectively. Total fat and triglyceride concentrations in liver were greatest in HF, lower in LF and HF+P, and lowest in the LF+P group. Therefore, the inclusion of soluble fibre in a high fat (or low fat) diet promoted increased satiety and decreased caloric intake, weight gain, adiposity, lipidaemia, leptinaemia and insulinaemia. These data support the potential of fermentable dietary fibre for weight loss and improving metabolic health in obesity.

Photoperiod regulates lean mass accretion, but not adiposity, in growing F344 rats fed a high fat diet.

In this study the effects of photoperiod and diet, and their interaction, were examined for their effects on growth and body composition in juvenile F344 rats over a 4-week period. On long (16L:8D), relative to short (8L:16D), photoperiod food intake and growth rate were increased, but percentage adiposity remained constant (ca 3-4%). On a high fat diet (HFD), containing 22.8% fat (45% energy as fat), food intake was reduced, but energy intake increased on both photoperiods. This led to a small increase in adiposity (up to 10%) without overt change in body weight. These changes were also reflected in plasma leptin and lipid levels. Importantly while both lean and adipose tissue were strongly regulated by photoperiod on a chow diet, this regulation was lost for adipose, but not lean tissue, on HFD. This implies that a primary effect of photoperiod is the regulation of growth and lean mass accretion. Consistent with this both hypothalamic GHRH gene expression and serum IGF-1 levels were photoperiod dependent. As for other animals and humans, there was evidence of central hyposomatotropism in response to obesity, as GHRH gene expression was suppressed by the HFD. Gene expression of hypothalamic AgRP and CRH, but not NPY nor POMC, accorded with the energy balance status on long and short photoperiod. However, there was a general dissociation between plasma leptin levels and expression of these hypothalamic energy balance genes. Similarly there was no interaction between the HFD and photoperiod at the level of the genes involved in thyroid hormone metabolism (Dio2, Dio3, TSHß or NMU), which are important mediators of the photoperiodic response. These data suggest that photoperiod and HFD influence body weight and body composition through independent mechanisms but in each case the role of the hypothalamic energy balance genes is not predictable based on their known function.

Dose-dependent effects of a soluble dietary fibre (pectin) on food intake, adiposity, gut hypertrophy and gut satiety hormone secretion in rats.

Soluble fermentable dietary fibre elicits gut adaptations, increases satiety and potentially offers a natural sustainable means of body weight regulation. Here we aimed to quantify physiological responses to graded intakes of a specific dietary fibre (pectin) in an animal model. Four isocaloric semi-purified diets containing 0, 3.3%, 6.7% or 10% w/w apple pectin were offered ad libitum for 8 or 28 days to young adult male rats (n = 8/group). Measurements were made of voluntary food intake, body weight, initial and final body composition by magnetic resonance imaging, final gut regional weights and histology, and final plasma satiety hormone concentrations. In both 8- and 28-day cohorts, dietary pectin inclusion rate was negatively correlated with food intake, body weight gain and the change in body fat mass, with no effect on lean mass gain. In both cohorts, pectin had no effect on stomach weight but pectin inclusion rate was positively correlated with weights and lengths of small intestine and caecum, jejunum villus height and crypt depth, ileum crypt depth, and plasma total glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY) concentrations, and at 8 days was correlated with weight and length of colon and with caecal mucosal depth. Therefore, the gut's morphological and endocrine adaptations were dose-dependent, occurred within 8 days and were largely sustained for 28 days during continued dietary intervention. Increasing amounts of the soluble fermentable fibre pectin in the diet proportionately decreased food intake, body weight gain and body fat content, associated with proportionately increased satiety hormones GLP-1 and PYY and intestinal hypertrophy, supporting a role for soluble dietary fibre-induced satiety in healthy body weight regulation.

Different types of soluble fermentable dietary fibre decrease food intake, body weight gain and adiposity in young adult male rats.

BACKGROUND: Dietary fibre-induced satiety offers a physiological approach to body weight regulation, yet there is lack of scientific evidence. This experiment quantified food intake, body weight and body composition responses to three different soluble fermentable dietary fibres in an animal model and explored underlying mechanisms of satiety signalling and hindgut fermentation. METHODS: Young adult male rats were fed ad libitum purified control diet (CONT) containing 5% w/w cellulose (insoluble fibre), or diet containing 10% w/w cellulose (CELL), fructo-oligosaccharide (FOS), oat beta-glucan (GLUC) or apple pectin (PECT) (4 weeks; n = 10/group). Food intake, body weight, and body composition (MRI) were recorded, final blood samples analysed for gut satiety hormones, hindgut contents for fermentation products (including short-chain fatty acids, SCFA) and intestinal tissues for SCFA receptor gene expression. RESULTS: GLUC, FOS and PECT groups had, respectively, 10% (P < 0.05), 17% (P < 0.001) and 19% (P < 0.001) lower food intake and 37% (P < 0.01), 37% (P < 0.01) and 45% (P < 0.001) lower body weight gain than CONT during the four-week experiment. At the end they had 26% (P < 0.05), 35% (P < 0.01) and 42% (P < 0.001) less total body fat, respectively, while plasma total glucagon-like peptide-1 (GLP-1) was 2.2-, 3.2- and 2.6-fold higher (P < 0.001) and peptide tyrosine tyrosine (PYY) was 2.3-, 3.1- and 3.0-fold higher (P < 0.001). There were no differences in these parameters between CONT and CELL. Compared with CONT and CELL, caecal concentrations of fermentation products increased 1.4- to 2.2-fold in GLUC, FOS and PECT (P < 0.05) and colonic concentrations increased 1.9- to 2.5-fold in GLUC and FOS (P < 0.05), with no consistent changes in SCFA receptor gene expression detected. CONCLUSIONS: This provides animal model evidence that sustained intake of three different soluble dietary fibres decreases food intake, weight gain and adiposity, increases circulating satiety hormones GLP-1 and PYY, and increases hindgut fermentation. The presence of soluble fermentable fibre appears to be more important than its source. The results suggest that dietary fibre-induced satiety is worthy of further investigation towards natural body weight regulation in humans.

Photoperiod regulates vitamin A and Wnt/ß-catenin signaling in F344 rats.

In seasonal mammals, growth, energy balance, and reproductive status are regulated by the neuroendocrine effects of photoperiod. Thyroid hormone (TH) is a key player in this response in a number of species. A neuroendocrine role for the nutritional factor vitamin A has not been considered, although its metabolic product retinoic acid (RA) regulates transcription via the same nuclear receptor family as TH. We hypothesized that vitamin A/RA plays a role in the neuroendocrine hypothalamus alongside TH signaling. Using a reporter assay to measure RA activity, we demonstrate that RA activity levels in the hypothalamus of photoperiod-sensitive F344 rats are reduced in short-day relative to long-day conditions. These lower RA activity levels can be explained by reduced expression of a whole network of RA signaling genes in the ependymal cells around the third ventricle and in the arcuate nucleus of the hypothalamus. These include genes required for uptake (Ttr, Stra6, and Crbp1), synthesis (Raldh1), receptor response (RAR), and ligand clearance (Crapb1 and Cyp26B1). Using melatonin injections into long-day rats, we show that the probable trigger of the fall in RA is melatonin. Surprisingly we also found RPE65 expression in the mammalian hypothalamus for the first time. Similar to RA signaling genes, members of the Wnt/ß-catenin pathway and NMU and its receptor NMUR2 are also under photoperiodic control. Our data provide strong evidence for a novel endocrine axis, involving the nutrient vitamin A regulated by photoperiod and melatonin and suggest a role for several new players in the photoperiodic neuroendocrine response.

An extremely rapid and simple DNA-release method for detection of M. tuberculosis from clinical specimens.

A single-step, 5-min lysis method was investigated as a rapid technique to extract genomic DNA from mycobacteria for PCR detection of M. tuberculosis directly from clinical specimens. Of 67 smear-positive clinical specimens, 64 (95.5%) were positive by PCR after this rapid extraction method.

Mnt1p and Mnt2p of Candida albicans are partially redundant alpha-1,2-mannosyltransferases that participate in O-linked mannosylation and are required for adhesion and virulence.

The MNT1 gene of the human fungal pathogen Candida albicans is involved in O-glycosylation of cell wall and secreted proteins and is important for adherence of C. albicans to host surfaces and for virulence. Here we describe the molecular analysis of CaMNT2, a second member of the MNT1-like gene family in C. albicans. Mnt2p also functions in O-glycosylation. Mnt1p and Mnt2p encode partially redundant alpha-1,2-mannosyltransferases that catalyze the addition of the second and third mannose residues in an O-linked mannose pentamer. Deletion of both copies of MNT1 and MNT2 resulted in reduction in the level of in vitro mannosyltransferase activity and truncation of O-mannan. Both the mnt2Delta and mnt1Delta single mutants were significantly reduced in adherence to human buccal epithelial cells and Matrigel-coated surfaces, indicating a role for O-glycosylated cell wall proteins or O-mannan itself in adhesion to host surfaces. The double mnt1Deltamnt2Delta mutant formed aggregates of cells that appeared to be the result of abnormal cell separation. The double mutant was attenuated in virulence, underlining the importance of O-glycosylation in pathogenesis of C. albicans infections.

Partial structure of glutamic acid and alanine-rich protein, a major surface glycoprotein of the insect stages of Trypanosoma congolense.

The tsetse fly transmitted salivarian trypanosome, Trypanosoma congolense of the subgenus Nanomonas, is the most significant of the trypanosomes with respect to the pathology of livestock in sub-Saharan Africa. Unlike the related trypanosome Trypanosoma brucei of the subgenus Trypanozoon, the major surface molecules of the insect stages of T. congolense are poorly characterized. Here, we describe the purification and structural characterization of the glutamic acid and alanine-rich protein, one of the major surface glycoproteins of T. congolense procyclic and epimastigote forms. The glycoprotein is a glycosylphosphatidylinositol-anchored molecule with a galactosylated glycosylphosphatidylinositol anchor containing an sn-1-stearoyl-2-l-3-HPO(4)-1-(2-O-acyl)-d-myo-inositol phospholipid moiety. The 21.6-kDa polypeptide component carries two large mannose- and galactose-containing oligosaccharides linked to threonine residues via phosphodiester linkages. Mass spectrometric analyses of tryptic digests suggest that several or all of the closely related glutamic acid and alanine-rich protein genes are expressed simultaneously in a T. congolense population growing in vitro.