The short chain fatty acid propionate stimulates GLP-1 and PYY secretion via free fatty acid receptor 2 in rodents

Background and Objectives:

The gut hormones peptide YY (PYY) and glucagon-like peptide 1 (GLP-1) acutely suppress appetite. The short chain fatty acid (SCFA) receptor, free fatty acid receptor 2 (FFA2) is present on colonic enteroendocrine L cells, and a role has been suggested for SCFAs in appetite regulation. Here, we characterise the in vitro and in vivo effects of colonic propionate on PYY and GLP-1 release in rodents, and investigate the role of FFA2 in mediating these effects using FFA2 knockout mice.

Methods:

We used Wistar rats, C57BL6 mice and free fatty acid receptor 2 knockout (FFA^−/−) mice on a C57BL6 background to explore the impact of the SCFA propionate on PYY and GLP-1 release. Isolated colonic crypt cultures were used to assess the effects of propionate on gut hormone release in vitro. We subsequently developed an in vivo technique to assess gut hormone release into the portal vein following colonic infusion of propionate.

Results:

Propionate stimulated the secretion of both PYY and GLP-1 from wild-type primary murine colonic crypt cultures. This effect was significantly attenuated in cultures from FFA2^−/− mice. Intra-colonic infusion of propionate elevated PYY and GLP-1 levels in jugular vein plasma in rats and in portal vein plasma in both rats and mice. However, propionate did not significantly stimulate gut hormone release in FFA2^−/− mice.

Conclusions:

Intra-colonic administration of propionate stimulates the concurrent release of both GLP-1 and PYY in rats and mice. These data demonstrate that FFA2 deficiency impairs SCFA-induced gut hormone secretion both in vitro and in vivo.

Effect of short chain fatty acids on the expression of free fatty acid receptor 2 (Ffar2), Ffar3 and early-stage adipogenesis

Adipose tissue has a major influence on insulin sensitivity. Stimulation of free fatty acid receptor 2 (FFAR2) has been proposed to influence adipocyte differentiation. We hypothesised that exposing preadipocytes to short chain fatty acids would induce earlier expression of nuclear receptors that co-ordinate adipogenesis, triglyceride accumulation and leptin secretion. 3T3-L1 preadipocytes were differentiated in the presence of 1 μM acetate, 0.1-10 μM propionate or vehicle control. In experiment 1, expression of Ffar2 and nuclear receptor mRNA was measured by quantitative PCR over 48 h following onset of differentiation. In experiment 2, extracellular leptin concentration and intracellular triglyceride content were measured at days 0, 2, 4, 6, 8 and 10 following the onset of differentiation. Control cells exhibited similar temporal dynamics of gene expression, triglyceride accumulation and leptin secretion as reported previously. We were unable to detect expression of Ffar3 mRNA at any stage of differentiation. Consistent with a lack of Ffar2 expression in the first 24 h of differentiation, acetate and propionate had no significant effect on nuclear receptor expression. Furthermore, acetate or propionate treatment did not alter leptin concentration or triglyceride content. In conclusion, we observed no significant effect of propionate or acetate on adipogenesis in 3T3-L1 cells using validated quantitative techniques.

Hepcidin levels in diabetes mellitus and polycystic ovary syndrome

AIM

Increased body iron is associated with insulin resistance. Hepcidin is the key hormone that negatively regulates iron homeostasis. We hypothesized that individuals with insulin resistance have inadequate hepcidin levels for their iron load.

METHODS

Serum concentrations of the active form of hepcidin (hepcidin-25) and hepcidin:ferritin ratio were evaluated in participants with Type 2 diabetes (n = 33, control subjects matched for age, gender and BMI, n = 33) and participants with polycystic ovary syndrome (n = 27, control subjects matched for age and BMI, n = 16). To investigate whether any changes observed were associated with insulin resistance rather than insulin deficiency or hyperglycaemia per se, the same measurements were made in participants with Type 1 diabetes (n = 28, control subjects matched for age, gender and BMI, n = 30). Finally, the relationship between homeostasis model assessment of insulin resistance and serum hepcidin:ferritin ratio was explored in overweight or obese participants without diabetes (n = 16).

RESULTS

Participants with Type 2 diabetes had significantly lower hepcidin and hepcidin:ferritin ratio than control subjects (P < 0.05 and P < 0.01, respectively). Participants with polycystic ovary syndrome had a significantly lower hepcidin:ferritin ratio than control subjects (P < 0.05). There was no significant difference in hepcidin or hepcidin:ferritin ratio between participants with Type 1 diabetes and control subjects (P = 0.88 and P = 0.94). Serum hepcidin:ferritin ratio inversely correlated with homeostasis model assessment of insulin resistance (r = -0.59, P < 0.05).

CONCLUSION

Insulin resistance, but not insulin deficiency or hyperglycaemia per se, is associated with inadequate hepcidin levels. Reduced hepcidin concentrations may cause increased body iron stores in insulin-resistant states.

Review: efficacy of alginate supplementation in relation to appetite regulation and metabolic risk factors: evidence from animal and human studies

This review provides a critical update on human and animal studies investigating the effect of alginate supplementation on appetite regulation, glycaemic and insulinemic responses, and lipid metabolism with discussion of the evidence on potential mechanisms, efficacy and tolerability. Dependent on vehicle applied for alginate supplementation, the majority of animal and human studies suggest that alginate consumption does suppress satiety and to some extent energy intake. Only one long-term intervention trial found effects on weight loss. In addition, alginates seem to exhibit beneficial influence on postprandial glucose absorption and insulin response in animals and humans. However, alginate supplementation was only found to have cholesterol-lowering properties in animals. Several mechanisms have been suggested for the positive effect observed, which involve delayed gastric emptying, increased viscosity of digesta and slowed nutrient absorption in the small intestine upon alginate gel formation. Despite reasonable efficacy and tolerability from the acute or short-term studies, we still realize there is a critical need for development of optimal alginate types and vehicles as well as studies on further long-term investigation on alginate supplementation in humans before inferring that it could be useful in the management of obesity and the metabolic syndrome.

Diabetes UK evidence-based nutrition guidelines for the prevention and management of diabetes

This article summarizes the Diabetes UK evidence-based guidelines for the prevention of Type 2 diabetes and nutritional management of diabetes. It describes the development of the recommendations and highlights the key changes from previous guidelines. The nutrition guidelines include a series of recommendations for the prevention of Type 2 diabetes, nutritional management of Type 1 and Type 2 diabetes, weight management, management of microvascular and macrovascular disease, hypoglycaemia management, and additional considerations such as nutrition support, end-of-life care, disorders of the pancreas, care of the older person with diabetes, nutrition provided by external agencies and fasting. The evidence-based recommendations were graded using the Scottish Intercollegiate Guidelines Network methodology and, in a small number of topic areas, where strong evidence was lacking, the recommendations were reached by consensus. The Diabetes UK 2011 guidelines place an emphasis on carbohydrate management and a more flexible approach to weight loss, unlike previous guidelines which were expressed in terms of recommendations for individual nutrient intakes. Additionally, the guidelines for alcohol have been aligned to national recommendations. The full evidence-based nutrition guidelines for the prevention and management of diabetes are available from: http://www.diabetes.org.uk/nutrition-guidelines.

Mortality and cancer incidence among British agricultural pesticide users

BACKGROUND

Although the acute effects of pesticides in humans are well known, uncertainty still exists about the health effects of chronic low-level exposure to pesticides.

AIMS

To compare mortality and cancer incidence experienced by a cohort of British pesticide users to that of the Great Britain (GB) population.

METHODS

The Pesticide Users Health Study (PUHS) comprises users of agricultural pesticides who have Certificates of Competence under the Control of Pesticides Regulations 1986. Participants were followed up between 1987 and 2004 (cancer incidence) or 2005 (mortality). Standardized mortality ratios (SMRs) and Standardized incidence ratios (SIRs) were estimated for outcomes of interest identified from the literature.

RESULTS

Altogether, 62,960 pesticide users were followed up for 829,709 person-years (to 31 December 2005). Most participants were male (94%) and based in England (86%). All-cause mortality was lower for both men [SMR 0.58, 95% confidence interval (CI) 0.55-0.60] and women (SMR 0.71, 95% CI 0.52-0.98) compared to the GB population. Mortality and incidence were below those expected for all cancers combined among men (SMR 0.71, 95% CI 0.66-0.77; SIR 0.85, 95% CI 0.81-0.90), particularly for cancers of the lip, oral cavity and pharynx, digestive organs and respiratory system. The incidence of testicular cancer, non-melanoma skin cancer and multiple myeloma were above expected. Mortality from injury by machinery was significantly above expected for men (SMR 4.21, 95% CI 2.11-8.42).

CONCLUSIONS

This study suggests that pesticide users in the PUHS are generally healthier than the national population but may have excesses of non-melanoma skin cancer, testicular cancer and multiple myeloma.

Pragmatic study of orlistat 60 mg on abdominal obesity

BACKGROUND/OBJECTIVES

It is well established that combining a reduced calorie, low-fat diet with the lipase inhibitor orlistat results in significantly greater weight loss than placebo plus diet. This weight loss is accompanied by changes in adipose tissue (AT) distribution. As 60 mg orlistat is now available as an over-the-counter medication, the primary objective of this study was to determine whether 60 mg orlistat is effective as a weight loss option in a free-living community population with minimal professional input.

METHODS

AT and ectopic lipid content were measured using magnetic resonance imaging and (1)H MR spectroscopy, respectively, in 27 subjects following 3 months treatment with orlistat 60 mg and a reduced calorie, low-fat diet.

RESULTS

Significant reductions in intra-abdominal AT (-10.6%, P=0.023), subcutaneous (-11.7% P<0.0001) and pericardial fat (-9.8%, P=0.034) volumes and intrahepatocellular lipids (-43.3%, P=0.0003) were observed. These changes in body fat content and distribution were accompanied by improvements in plasma lipids and decreases in blood pressure and heart rate.

CONCLUSION

These findings suggest that over-the-counter 60 mg orlistat, in combination with the type of advice a subject could expect to be given when obtaining 60 mg orlistat in a community setting, does indeed result in potentially clinically beneficial changes in body composition and risk factors for metabolic diseases.

Abstract LB-307: Hyaluronan deposition correlates with poor survival in pancreatic cancer

Hyaluronan (HA) is an extracellular matrix component that plays an important role in a diverse range of cellular processes including proliferation, tissue hydration, cell motility, inflammation, angiogenesis, and malignancy. Increased HA deposition is a characteristic of many desmoplastic tumors. High HA levels have been correlated with poor prognosis in some cancer types, including gastric, colorectal, breast, ovarian, and bladder cancers. Considering the high desmoplastic stromal content of pancreatic tumors, we hypothesized that high HA levels may contribute to poor prognosis or survival in pancreatic cancer. Utilizing a biotinylated HA binding protein-based staining method in a tissue microarray constructed from resected pancreatic tumor tissues, we assessed HA-specific staining in 43 pancreatic ductal adenocarcinoma samples for which patient survival had been followed for more than eight years. We observed HA staining primarily in the peritumoral, or stromal, compartment of the tumor tissue samples. 100% of the patient tumors stained positive in at least some fraction of the tissue area (stroma) for HA. The staining was scored according to the percentage area of HA-positivity, relative to total tissue area. We observed low (&lt;40%) and high (≥40%) levels of stromal HA in 11 and 32 patient samples, respectively. We tested our hypothesis with the log-rank test and found that the survival rate was significantly lower among patients with high HA (P&lt;0.05). The median survival among those patients with high HA was 299 days, and 738 days for those with low HA (the difference in median survival between the two patient groups is 439 days). These results suggest that HA levels in pancreatic adenocarcinoma patients may be predictive of survival. Because HA functions in maintaining high tumoral interstitial fluid pressure, resulting in vascular compression and limited tumor-drug access, our results also suggest that HA may serve as a potential therapeutic target in pancreatic cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-307. doi:10.1158/1538-7445.AM2011-LB-307

Abstract 2265: Expression of hyaluronan in human cancer tissue: A predictive biomarker for PEGPH20-mediated therapy

Background: Hyaluronan (HA), a ubiquitous, high-molecular-mass polysaccharide in the precellular and extracellular matrix, is frequently elevated in malignancy, and associated with aggressive disease. Interaction of HA and tumor cells may activate receptor tyrosine kinases, enhance drug resistance, and facilitate tumor progression. A pegylated recombinant human PH20 hyaluronidase (PEGPH20) has been developed to systemically target tumors that accumulated with HA. Systemic PEGPH20 administration in mice bearing PC3 tumors induced a decrease in tumor interstitial fluid pressure (IFP), a decrease in tumor water content, and an increase in tumor vascular volume by enzymatically depleting the HA from the extracellular tumor microenvironment and resulted in significant tumor growth inhibition. PEGPH20 therefore represents an innovative potential treatment approach that may provide improved therapeutic outcomes for cancer patients.

Methods: The present study investigated the expression of HA in paraffin embedded human tissue from 9 tumor types as well as corresponding normal tissue by immunohistochemical staining of BioMax tissue arrays with biotinylated HA binding protein (HABP) as a probe. Staining intensity was quantified using Aperio Spectrum plus software. The correlation between HA expression and PEGPH20 response has also been explored using established preclinical models.

Results: Strong HA expression was found in 87% of pancreatic, 64% of breast, 50% of multiple myeloma, 46% of NSCLC, 39% of gastric, and 22% of prostate cancer tissues, when compared with corresponding normal tissue (p&lt;0.05). BxPc3 (HA high), MIA PaCa-2 (HA low) and AsPC-1 (HAlow) pancreatic tumor xenografts were evaluated for tumor growth inhibition (TGI) after systemic PEGPH20 treatment and TGI's of 25%, 9% and 15% were observed respectively. In addition, 3 prostate cancers, PC3 (HA high), MatLylu (HA high) and Du145 (HA low) were also evaluated in xenografts with significant growth inhibition shown for PC3 (72%) and MatLylu (34%). Systemic PEGPH20 treatment also induced tumor growth inhibition (60%) for 4T1 (HA high) breast cancer.

Conclusion: Accumulation of HA compared to normal tissue was commonly observed and most frequent in pancreatic adenocarcinomas (87%). Furthermore, accumulation of HA was shown to predict response to PEGPH20 therapy in xenograft models (R2=0.805, p&lt;0.01). This work provides strong rationale for exploring efficacy of PEGPH20 in clinical trials.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2265.

Adipose tissue, adipocytes and the circadian timing system

Circadian clocks time the daily occurrence of multiple aspects of behaviour and physiology. Through studies of chronic misalignment between our internal clocks and the environment (e.g. during shift work), it has long been postulated that disruption of circadian rhythms is detrimental to human health. Recent advances in understanding of the cellular and molecular basis of mammalian circadian timing mechanisms have identified many key genes involved in circadian rhythm generation and demonstrated the presence of clocks throughout the body. Furthermore, clear links between sleep, circadian rhythms and metabolic function have been revealed, and much current research is studying these links in more detail. Here, we review the evidence linking circadian rhythms, clock genes and adipose biology. We also highlight gaps in our understanding and finally suggest avenues for future research.

Evaluation of attendance and weight loss in an intensive weight management clinic compared to standard dietetic care

BACKGROUND

With increasing rates of obesity, the effectiveness of weight reduction programmes come under increasing scrutiny. This nonrandomized study aimed to review the effectiveness of two weight loss clinics in terms of percent and rate of weight loss, and attendance.

METHODS

Data were collected on consecutive obese patients, attending either an intensive weight management clinic (IWMC) or a general dietetic outpatient clinic. The IWMC had a structured approach with six once-a-month appointments, a signed agreement to attend, an initial screening of readiness to change and consistent advice from one dietitian. The general clinic was less structured, had more ad hoc follow up and did not guarantee one dietitian.

RESULTS

Seventy percent of patients referred were female [mean (SD) age 48 (14.2) years]. Thirty-three percent (103/313) of all patients referred did not book an appointment. Of those attending with a body mass index > or = 32 kg m(-2), 55% were seen in the general and 45% in the intensive clinic, but only 19% and 53%, respectively, completed the programmes. The total amount and rate of weight loss did not differ significantly between clinics. However, analysis using the last recorded weight revealed a median weight reduction of 1.8% (interquartile range = -5.6-0) at the median rate of -0.4 kg month(-1) (-1-0) in the intensive clinic, compared to no overall weight loss in the general clinic (P < or = 0.001).

CONCLUSIONS

A more structured approach and initial screening of readiness to change is likely to achieve better weight loss results and therefore will comprise a better use of dietetic time than including obese patients in general clinics.

Clinical trial: normal diet vs. partial replacement with oral E028 formula for the prevention of gastrointestinal toxicity in cancer patients undergoing pelvic radiotherapy

BACKGROUND

Acute gastrointestinal symptoms affect 90% of patients during pelvic radiotherapy. Elemental diet is protective in animal models. A nonrandomized study suggested benefit from a partial elemental diet. A pilot study suggested that radiotherapy patients only tolerate oral elemental diet comprising one-third of total calories for 3 weeks.

AIM

To assess the feasibility and efficacy of replacing one-third of normal diet with elemental diet during the first 3 weeks of pelvic radiotherapy in reducing acute gastrointestinal toxicity.

METHODS

Patients were randomized to elemental diet or no intervention. Toxicity was assessed using the Inflammatory Bowel Disease Questionnaire, Vaizey Incontinence scale and Radiation Therapy Oncology Group tool. Faecal calprotectin measured intestinal mucosal inflammation.

RESULTS

Twenty-nine women and 21 men, median age 61.5 years were randomized. Patients taking elemental diet did not have lower gastrointestinal toxicity ratings or inflammatory markers (P > 0.2). The mean dose taken was 21% (2-36%) of total caloric requirements.

CONCLUSIONS

Patients cannot tolerate large volumes of oral elemental diet. The quantities consumed in this study produced no therapeutic benefit. Future studies should aim to replace a higher proportion of nutritional intake for a longer duration of radiotherapy treatment.

A new method of energy prescription to improve weight loss

Clinical outcome audit was carried out on two groups of obese out-patients for a 3-month follow-up period. In the first audit group of 35 patients (A1), energy intake was prescribed by diet history, whereas in the second audit group of 27 patients (A2) energy intake was prescribed from an estimate of individual energy requirements based on age, sex, and activity. There was no significant difference in age or initial BMI between the two groups and the failure-to-attend rate was the same in each group. Patients in Group A2 received a significantly higher energy prescription (P<0.001) than Group A1, but this was still significantly more restricted than the recommended 500 kcal energy deficit from energy expenditure (P<0.05). Weight loss was significant in both groups, but was greater in Group A2 than in Group A1. There was no significant correlation between weight loss and energy deficit. In a selected group of patients from Group A2 who were prescribed energy intake close to the recommended deficit of 500 kcal, weight loss was found to be significantly greater (P<0.05) when compared to the weight loss in Group A1. Results suggest that a diet prescription with an energy deficit below the estimated energy requirements does not lead to greater weight loss and probably reduces compliance. Estimating individual energy requirements rather than using dietary assessment may improve weight loss.