Tom Preston

Reduced total energy expenditure and physical activity in cachectic patients with pancreatic cancer can be modulated by an energy and protein dense oral supplement enriched with n-3 fatty acids

The aim of the study was to assess the total energy expenditure (TEE), resting energy expenditure (REE) and physical activity level (PAL) in home-living cachectic patients with advanced pancreatic cancer. The influence of an energy and protein dense oral supplement either enriched with or without the n-3 fatty acid eicosapentaenoic acid (EPA) and administered over an 8-week period was also determined. In total, 24 patients were studied at baseline. The total energy expenditure was measured using doubly labelled water and REE determined by indirect calorimetry. Patients were studied at baseline and then randomised to either oral nutritional supplement. Measurements were repeated at 8 weeks. At baseline, REE was increased compared with predicted values for healthy individuals (1387(42) vs 1268(32) kcal day−1, P=0.001), but TEE (1732(82) vs 1903(48) kcal day−1, P=0.023) and PAL (1.24(0.04) vs 1.50) were reduced. After 8 weeks, the REE, TEE and PAL of patients who received the control supplement did not change significantly. In contrast, although REE did not change, TEE and PAL increased significantly in those who received the n-3 (EPA) enriched supplement. In summary, patients with advanced pancreatic cancer were hypermetabolic. However, TEE was reduced and this was secondary to a reduction in physical activity. The control energy and protein dense oral supplement did not influence the physical activity component of TEE. In contrast, administration of the supplement enriched with EPA was associated with an increase in physical activity, which may reflect improved quality of life.

Effects of targeted delivery of propionate to the human colon on appetite regulation, body weight maintenance and adiposity in overweight adults.

Objective The colonic microbiota ferment dietary fibres, producing short chain fatty acids. Recent evidence suggests that the short chain fatty acid propionate may play an important role in appetite regulation. We hypothesised that colonic delivery of propionate would increase peptide YY (PYY) and glucagon like peptide-1 (GLP-1) secretion in humans, and reduce energy intake and weight gain in overweight adults. Design To investigate whether propionate promotes PYY and GLP-1 secretion, a primary cultured human colonic cell model was developed. To deliver propionate specifically to the colon, we developed a novel inulin-propionate ester. An acute randomised, controlled cross-over study was used to assess the effects of this inulin-propionate ester on energy intake and plasma PYY and GLP-1 concentrations. The long-term effects of inulin-propionate ester on weight gain were subsequently assessed in a randomised, controlled 24-week study involving 60 overweight adults. Results Propionate significantly stimulated the release of PYY and GLP-1 from human colonic cells. Acute ingestion of 10 g inulin-propionate ester significantly increased postprandial plasma PYY and GLP-1 and reduced energy intake. Over 24 weeks, 10 g/day inulin-propionate ester supplementation significantly reduced weight gain, intra-abdominal adipose tissue distribution, intrahepatocellular lipid content and prevented the deterioration in insulin sensitivity observed in the inulin-control group. Conclusions These data demonstrate for the first time that increasing colonic propionate prevents weight gain in overweight adult humans. Trial registration number NCT00750438.

Albumin concentrations are primarily determined by the body cell mass and the systemic inflammatory response in cancer patients with weight loss

The association between hypoalbuminemia and poor prognosis in patients with cancer is well recognized. However, the factors that contribute to the fall in albumin concentrations are not well understood. In the present study, we examined the relationship between circulating albumin concentrations, weight loss, the body cell mass (measured using total body potassium), and the presence of an inflammatory response (measured using C-reactive protein) in male patients (n = 40) with advanced lung or gastrointestinal cancer. Albumin concentrations were significantly correlated with the percent ideal body weight (r = 0.390, p < 0.05), extent of reported weight loss (r = -0.492, p < 0.01), percent predicted total body potassium (adjusted for age, height, and weight, r = 0.686, p <0.001), and log10 C-reactive protein concentrations (r = -0.545, p < 0.001). On multiple regression analysis, the percent predicted total body potassium and log10C-reactive protein concentrations accounted for 63% of the variation in albumin concentrations (r2 = 0.626, p < 0.001). The interrelationship between albumin, body cell mass, and the inflammatory response is consistent with the concept that the presence of an ongoing inflammatory response contributes to the progressive loss of these vital protein components of the body and the subsequent death of patients with advanced cancer.

Formation of short chain fatty acids by the gut microbiota and their impact on human metabolism

ABSTRACT The formation of SCFA is the result of a complex interplay between diet and the gut microbiota within the gut lumen environment. The discovery of receptors, across a range of cell and tissue types for which short chain fatty acids SCFA appear to be the natural ligands, has led to increased interest in SCFA as signaling molecules between the gut microbiota and the host. SCFA represent the major carbon flux from the diet through the gut microbiota to the host and evidence is emerging for a regulatory role of SCFA in local, intermediary and peripheral metabolism. However, a lack of well-designed and controlled human studies has hampered our understanding of the significance of SCFA in human metabolic health. This review aims to pull together recent findings on the role of SCFA in human metabolism to highlight the multi-faceted role of SCFA on different metabolic systems.

Remote sensing of the water quality of shallow lakes: A mixture modelling approach to quantifying phytoplankton in water characterized by high‐suspended sediment

Remote sensing has the potential to provide truly synoptic views of water quality, in particular, the spatial distributions of phytoplankton. Whilst the spectral capabilities of satellites used in ocean colour work have improved significantly over recent years, the application of satellite remote sensing to lake water is constrained by the need for high spatial resolution image data and thus remains limited by spectral resolution capabilities. This becomes a significant problem when attempting to quantify chlorophyll a (Chl a) in waters characterized by high and heterogeneous suspended sediment concentrations (SSC). The SSC dominates the spectral reflectance, masking the spectral influence from other components in broad spectral band systems, making Chl a determination from remote sensing imagery difficult. This paper presents a linear mixture modelling approach to derive accurate estimates of Chl a from Landsat Thematic Mapper (TM) imagery. This approach was tested in Lake Balaton, Europes largest shallow lake characterized by high suspended sediment and, until recently, frequent eutrophic and hypereutrophic episodes. The last significant bloom occurred in September of 2000 and a Landsat TM image was acquired for 11th September, during which ground reference data of water quality was collected. The modelled image‐derived results of Chl a demonstrate an excellent correspondence (r2 = 0.95) between the ground‐based measurements of Chl a, and yield considerable detail of lake phytoplankton distributions. The September 2000 calibration was then successfully applied to a July 1994 Landsat TM image and validated with Chl a data collected coincidently within two days of the image. The comparability between water sample data and image results demonstrates that there is temporal stability and robustness in the approach and calibration described.

Pancreatic cancer as a model: inflammatory mediators, acute-phase response, and cancer cachexia

Abstract. Patients with pancreatic cancer frequently develop the syndrome of cancer cachexia. Pro-inflammatory cytokines have been strongly implicated in the pathogenesis of this syndrome. In patients with pancreatic cancer an acute-phase response (an index of pro-inflammatory cytokine activity) is associated with accelerated weight loss, hypermetabolism, anorexia, and a shortened duration of survival. However, little is known about the primary significance of the acute-phase response in terms of altered hepatic export protein synthesis rates and its potential impact on the bodys nitrogen economy. In a recent series of studies on weight-losing pancreatic cancer patients with hypoalbuminemia we have demonstrated albumin synthesis to be unaltered whereas fibrinogen synthesis is increased two- to threefold compared with healthy controls. Because of the mismatch in amino acid composition between the bodys main labile amino acid reserve (skeletal muscle) and that of acute-phase proteins, these results lend support to the concept that in pancreatic cancer the reprioritization of body protein metabolism during an acute-phase response may well be a significant factor in the loss of lean tissue in these patients.

Albumin synthesis rates are not decreased in hypoalbuminemic cachectic cancer patients with an ongoing acute-phase protein response.

OBJECTIVE To determine whether suppression of albumin synthesis contributes to the hypoalbuminemia observed in weight-losing cancer patients with evidence of an ongoing acute-phase protein response (APPR). BACKGROUND DATA Proinflammatory cytokines such as tumor necrosis factor (TNF) and interleukin 6 (IL-6) are known to downregulate albumin synthesis and increase acute-phase protein production in isolated hepatocytes. However, whether albumin synthesis is suppressed in hypoalbuminemic cancer patients with evidence of an ongoing acute-phase response is unknown. METHODS Albumin synthesis rates were determined in six healthy controls and in six weight-losing pancreatic cancer patients with an ongoing APPR using a flooding dose technique with [2H5]-phenylalanine. The presence of an APPR was defined as a serum C-reactive protein concentration >10 mg/L. Serum cytokines (TNF, IL-6) and soluble TNF receptors (sTNF-R 55 and 75), along with serum cortisol and insulin, were also measured in both groups. RESULTS Cancer patients had reduced serum albumin (median 32 [range, 23-36] vs. 42 g/L [40-45]; p < 0.01) and increased serum C-reactive protein concentrations (72 [23-126] vs. <5 mg/L; p < 0.01) when compared with controls. TNF was not detected in either group. sTNF-R 55 levels were significantly elevated in the cancer patients (3.8 [1.9-8.1] vs. 1.2 pg/mL [0.9-2.2]; p < 0.01). Circulating IL-6, insulin, and cortisol concentrations were not significantly different between the groups. The intravascular albumin mass was lower (88 [56-93] vs. 133 g [105-177]; p < 0.01), but the intravascular albumin fractional synthetic rate was higher (13.9 [13.5-18.5] vs. 10.3%/d [71-11.3]; p < 0.01) in the cancer patients compared with the controls. The total intravascular albumin synthetic rate was, however, similar between the two groups (12.7 [7.7-15.7] vs. 11.7 g/d [8.5-18.7]; p NS). CONCLUSIONS In weight-losing pancreatic cancer patients with evidence of an ongoing APPR, hypoalbuminemia is not caused by a decreased rate of albumin synthesis.

Butyrate production from oligofructose fermentation by the human faecal flora: what is the contribution of extracellular acetate and lactate?

Butyrate is an important substrate for maintenance of colonic health and oligofructose fermentation by human faecal bacteria can increase butyrate production in vitro. However, oligofructose appears to be fermented by mainly acetate and lactate-producing bacteria rather than butyrate-producing bacteria. Isotope labelling studies using [U-(13)C(6)]glucose were used to show that (13)C(2) and (13)C(4) were the major labelled butyrate species produced from glucose fermentation, via [(13)C(2)]acetate-acetyl CoA as intermediate. Bacterial interconversion reactions were quantified and acetate conversion to butyrate and lactate conversion to acetate, propionate and butyrate were observed. Addition of oligofructose to faecal batch cultures significantly increased butyrate production. Of the newly synthesised butyrate from oligofructose fermentation, 80 % was derived from interconversion of extracellular acetate and lactate, with acetate being quantitatively more significant. Carbohydrates, such as oligofructose, have prebiotic properties. In addition, oligofructose selectively stimulates the bacterial conversion of acetate and lactate to butyrate. Carbohydrates with similar properties represent a refinement of the prebiotic definition, termed butyrogenic prebiotics, because of their additional functionality.

Elevated circulating interleukin-6 is associated with an acute-phase response but reduced fixed hepatic protein synthesis in patients with cancer.

It has been suggested that, as part of the inflammatory response to the presence of a tumor, various cytokines are produced and these induce hepatic synthesis of acute-phase proteins (APP). Under these circumstances it is not known what changes occur in the fixed component of hepatic protein synthesis. The aim of this study was to compare circulating interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor (TNF) concentrations and fixed hepatic protein synthesis rates in a group of healthy controls (n = 6) with a group of patients with an established APP response secondary to hepatic metastasis from colorectal cancer (n = 6). Fixed hepatic protein synthesis rates were measured following a primed, constant 20-hour infusion of 15N-glycine. The liver was biopsied at laparotomy. The APP response was assessed by serum C-reactive protein concentration and cytokines were assayed by a combination of immunoassay and bioassay. The patients with advanced cancer and an on-going APP response had elevated circulating IL-6 concentrations (p less than 0.01). Rates of fixed hepatic protein synthesis were 30% lower than those observed in controls (p less than 0.01). These findings demonstrate that in patients with hepatic metastasis, although the synthesis of certain acute-phase export proteins can be increased, fixed protein synthesis is reduced. Whether these changes in the distribution of hepatic protein synthesis are mediated by IL-6 will require further investigation.

Longitudinal study of body cell mass depletion and the inflammatory response in cancer patients

There is recent evidence that the inflammatory response may be important in the disproportionate loss of body cell mass in cancer patients. To examine this further, 18 male patients with lung or gastrointestinal cancer were studied over a 12-week period. In addition to weight, anthropometry, C-reactive protein (marker of the inflammatory response), albumin, and total body potassium were measured at baseline and 12 weeks. When those patients who lost total body potassium were compared with those who had not, there was a significant increase in the baseline and 12-week C-reactive protein concentrations (p < 0.05). The reduction in total body potassium was also associated with a reduction in triceps skinfold thickness (p < 0.05). There were significant correlations between the mean C-reactive protein concentration and the relative (r = -0.846, p < 0.001) and absolute (r = -0.806, p < 0.001) change in total body potassium over the follow-up period. This study demonstrates the association of a chronic inflammatory response with the rate of loss of body cell mass observed in cancer patients.