Skip to main content Accessibility help
×
Home

Information:

  • Access
  • Cited by 10

Actions:

      • Send article to Kindle

        To send this article to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about sending to your Kindle.

        Note you can select to send to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

        Find out more about the Kindle Personal Document Service.

        Increased acylated plasma ghrelin, but improved lipid profiles 24-h after consumption of carob pulp preparation rich in dietary fibre and polyphenols
        Available formats
        ×

        Send article to Dropbox

        To send this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Dropbox.

        Increased acylated plasma ghrelin, but improved lipid profiles 24-h after consumption of carob pulp preparation rich in dietary fibre and polyphenols
        Available formats
        ×

        Send article to Google Drive

        To send this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Google Drive.

        Increased acylated plasma ghrelin, but improved lipid profiles 24-h after consumption of carob pulp preparation rich in dietary fibre and polyphenols
        Available formats
        ×
Export citation

Abstract

We have recently shown that a polyphenol-rich insoluble dietary fibre preparation from carob pulp (Ceratonia siliqua L; carob fibre) decreased postprandial acylated ghrelin, TAG and NEFA during an acute liquid meal challenge test. However, delayed effects of carob fibre consumption are unknown. Therefore, a randomized controlled crossover study in nineteen healthy volunteers consuming foods with or without 50 g carob fibre was conducted. On the subsequent day (day 2), glucose, TAG, total and acylated ghrelin as well as insulin, NEFA and leptin were assessed at baseline and at timed intervals for 300 min after ingestion of standardized bread. Consumption of carob fibre-enriched foods did not affect fasting concentrations of glucose, TAG, total ghrelin, NEFA, insulin and leptin. Fasting acylated ghrelin was increased on the day subsequent to carob fibre consumption compared with control (P = 0·046). After consumption of the standard bread on day 2, glucose response (P = 0·029) was increased, and TAG (P = 0·033) and NEFA (P < 0·001) responses were decreased compared with control. Postprandial responses of total and acylated ghrelin, insulin and leptin on day 2 were unaffected by carob fibre consumption the previous day. In conclusion, an increase in total and acylated plasma ghrelin accompanied by enhanced lipid metabolism after carob fibre consumption suggests higher lipid utilization and suppressed lipolysis on the day subsequent to carob fibre consumption. However, elevated glucose levels after carob fibre consumption need to be addressed in future studies.

Epidemiological studies clearly show that a high intake of insoluble fibre is associated with a low risk for CVD and diabetes13. Beneficial effects of insoluble dietary fibre are also discussed in the context of consumption of whole grain, containing further bioactive compounds such as polyphenols, antioxidants or vitamins. As another potential mechanism for the beneficial effects of dietary fibre, fermentation processes in the colon are discussed resulting in the production of SCFA4, 5. Polyphenols have been shown to reduce food intake, to lower leptin concentrations6 and to promote fat oxidation in rats7. Recently, we showed that the consumption of a polyphenol-rich insoluble dietary fibre preparation from carob pulp (Ceratonia siliqua L; carob fibre) acutely decreased postprandial TAG and NEFA concentrations, while increasing fat oxidation during a liquid meal challenge test8. Elevated circulating TAG and NEFA play a key role in the development of insulin resistance9. Impaired whole body insulin resistance is characterized by a lowered ability of skeletal muscle to oxidize fatty acids9. Therefore, functional foods lowering circulating NEFA by increasing fat oxidation might be of interest for the prevention and treatment of diabetes and obesity.

Obesity is the result of a positive energy balance. Among peripheral hormones regulating energy balance, the orexigenic ghrelin and the anorexigenic leptin are of special interest1015. Ghrelin is synthesized and secreted mainly from the fundic region of the stomach and stimulates food intake16. It has been proposed that ghrelin secretion in man is directly regulated by leptin restraint17. Leptin is a hormone that is predominantly secreted by adipose tissue18, 19, but it is also synthesized and secreted in the stomach by fundic glands20. Approximately 25 % of circulating leptin is originated from the stomach21. Leptin is primarily involved in energy homeostasis and satiety. Leptin concentrations in the circulation are increased in proportion to fat mass and circulating leptin conveys information to the hypothalamus regarding the amount of energy stored in adipose tissue, suppressing appetite and affecting energy expenditure12. Recently, we reported that the consumption of carob fibre was associated with an acute decrease in acylated plasma ghrelin during a liquid meal challenge test8. However, no information is available about delayed effects of carob fibre on acylated and total ghrelin and its effects on leptin secretion.

The aim of the study was to investigate delayed effects of carob fibre consumption on: (1) fasting levels; (2) postprandial response of glucose, insulin, NEFA, TAG, leptin and total and acylated ghrelin concentration. We also investigated whether carob consumption is associated with fermentation processes in the colon resulting in the production of SCFA.

Methods

Study design and subjects

This was a randomized crossover trial with two sessions lasting 300 min each, separated by intervals of at least 1 week. Nineteen healthy adults were recruited. Exclusion criteria were history of chronic diseases, dyslipidaemia, impaired glucose tolerance, intentional weight loss within 3 months prior to the study, extreme sports, history of chronic alcohol abuse and any medication influencing glucose or lipid metabolism. The Ethics Committee of the University of Potsdam approved the study protocol. Written informed consent was obtained from all participants before starting the study.

Habitual alcohol intake

A semi-quantitative, self-administered 4-d food record was used to assess alcohol intake of the study participants. The assessment was conducted three times and the results of the three food records (three × 4 d) were averaged. Trained staff delivered the record and subjects were instructed to record their entire food intake at the time of consumption. Alcohol intake was coded on the basis of the German Food Code and Nutrient Data Base BLS II.322. The accuracy and validity of energy intake estimated by the food record was validated against total energy expenditure estimated by doubly labelled water technique23.

Body composition

Anthropometric data of the participants were collected at the beginning of the study. Body weight was assessed using an electronic calibrated scale to the nearest 0·1 kg (Soehnle, Murrhardt, Germany). Body height was determined with a GPM anthropometer (Siber & Hegner, Zurich, Switzerland) to the nearest 0·1 cm. BMI was calculated as body weight (kg)/ height (m)2.

Dietary intervention

On the day preceding the blood sampling sessions (day 1), foods with or without a total of 50 g carob fibre were provided in a randomized order containing a total energy of 6228 v. 6279 kJ (Table 1). Carob fibre, a preparation from carob pulp (Caromax, Nutrinova, Frankfurt, Germany), contained (g/100 g): 5·8 simple carbohydrates; 5·2 protein; 0·2 fat. The total fibre content was 74·6 g per 100 g carob fibre preparation corresponding to 68·4 g insoluble and 6·2 g soluble fibre. The content of water-soluble polyphenols of the preparation was 2·84 g per 100 g; the content of extractable polyphenols by organic solvents was 0·39 g per 100 g24. The major polyphenol compounds of carob fibre were gallic acid, gallotannins and flavonol glycosides24.

Table 1 Composition of the dietary intervention and total dietary intake of the day preceding the blood sampling

(Mean values with their standard errors)

* P < 0·05 between treatments.

Including all foods consumed (i.e. standardized foods provided and additional free-choice foods).

For details of subjects and procedures, see Methods.

The participants were able to distinguish between meals containing carob fibre v. placebo by taste and colour. However, laboratory staff were not informed about the treatments of participants. Participants were advised to consume the foods provided for breakfast, dinner and lunch. Participants were allowed to consume additional foods but the additional foods had to be the same in both treatments. Foods rich in polyphenols, such as red wine, olive oil or cacao products, were not allowed. Dietary intake was assessed using an estimated food record23.

In the morning of study day 2 after a 10 h overnight fast, subjects consumed 103 g standardized white bread within 5 min. The energy content of the white bread was 1027 kJ with a nutrient content of 50·0 g carbohydrates, 7·7 g proteins, 1·5 g fat and 2·9 g dietary fibre.

Blood sampling and analyses

On study day 2, an indwelling catheter was inserted into an antecubital vein of the subjects and blood samples were collected before and 15, 30, 45, 60, 75, 90, 120, 150, 180, 210, 240, 270 and 300 min after consumption of the standardized bread. On each session, a total of 180 ml blood was collected. Postprandial measurements were made within a 300-min time period to ensure complete meal absorption independent of the carob fibre enrichment as a routine procedure comparable with other studies25.

For serum separation, blood was collected in tubes containing a serum clot activator and allowed to clot. To obtain plasma, blood was collected in EDTA-containing tubes and immediately processed. Serum and plasma tubes were centrifuged at 1500 g for 10 min at 4°C and supernatants were obtained and stored at − 40°C until analysis. For measurement of total and acylated ghrelin, plasma was collected in tubes containing EDTA and 500 U Aprotinin (Bayer, Leverkusen, Germany) per ml whole blood. For stabilization, plasma supernatant was acidified with 1 mmol/l HCl and then stored at − 40°C.

Plasma total ghrelin was measured by a commercial RIA, which utilizes 125I-labelled ghrelin and a ghrelin antiserum to determine the concentration of total ghrelin in plasma by a double antibody/polyethylenglycol technique (GHRT-89HK; Linco Research, St. Charles, MO, USA). The sensitivity of the method was 93 pg/ml. There was no cross-reaction with ghrelin 1-10, motilin-related peptide, glucagon, leptin or insulin. The intra- and inter-assay CV were 10·0 % and 14·7 %, respectively. Recovery was calculated as 96 %.

Plasma active ghrelin determination was performed using RIA (GHRA-88HK, Linco Research) that utilizes 125I-labelled ghrelin as a tracer and an antibody (raised in guinea pigs) that is specific for the biological active form of ghrelin with the octanoyl group on serine 3. The sensitivity of the method was 7·8 pg/ml. There was no cross-reaction with ghrelin 14–28, motilin-related peptide, glucagon, leptin or insulin. The intra- and inter-assay CV were 6·7 % and 9·6 %, respectively. Recovery was calculated as 114 %.

Plasma glucose was measured in duplicate by the hexokinase method using commercially available colorimetric reagents (ADVIA® 1650 Chemistry System; GLUH, Bayer, Leverkusen, Germany) with an intra-assay CV of 1·2 %.

Serum insulin was determined by ADVIA Centaur Immunoassay (Bayer) with an intra-assay CV of 2·6 %.

Plasma TAG were analysed using the enzymatic colorimetric agents TRIG for the ADVIA® Chemistry System 1650 (Bayer). The intra-assay CV was 1·2 %.

Serum NEFA were analysed using an enzymatic colorimetric method (ASC-ACOD method; Wako Chemicals, Neuss, Germany) with an inter-assay CV of 2·7 %.

Leptin concentration in serum was measured using an immunofluorometric assay as described previously26. Microtitre plates coated with anti-leptin mAb 4D3 (500 ng/well) were washed and standards or samples were pipetted into each well together with 50 ng biotinylated anti-leptin mAb 6D9 in 0·175 ml assay buffer. After an overnight incubation at 4°C, the plates were washed and streptavidin-europium was added. After an additional incubation for 30 min, plates were washed again, enhancement solution was added and the signal measured after 15 min using the DELFIA (Wallac, Turku, Finland). Within assay variability (CV %) was 7·4 %, 4·3 % and 5·6 % at leptin concentrations of 0·8 ng/ml, 2·5 ng/ml and 15·3 ng/ml, respectively. Between assay CV % at the same concentrations was 8·3, 5·2 and 5·9 %, respectively.

Serum total cholesterol was analysed using the CHOD/PAP method (ABX Diagnostics Cholesterol; ABX Diagnostics, Montpellier, France) with an intra-assay CV of 0·8 %.

Serum HDL-cholesterol was analysed using a colorimetric test (ABX Diagnostics HDL Cholesterol Direct; ABX Diagnostics) with an intra-assay CV of 1·3 %. LDL-cholesterol was calculated according to Friedewald27.

Breath hydrogen analysis

To control for dietary compliance, air breath samples were collected as a marker of colonic fermentation before and 30, 60, 90, 120, 150, 180, 210, 240, 270 and 300 min after consumption of the standardized bread on day 2 and measured using a Breath Hydrogen Analyzer (Quintron Model-12i-Microlyzer; Quintron Instruments, Milwaukee, WI, USA). All subjects were capable of producing breath H.

Determination of SCFA

For estimation of SCFA using GC, suspensions prepared from fresh faeces, obtained from the two defecations following day 1, were mixed with water (material/water 1:5 wt/vol.) and homogenized and SCFA were determined as described previously28. The GC system (Hewlett-Packard, Waldbronn, Germany) consisted of a HP gas-chromatograph 5890 Series II, HP 7673 GC/SFC Injector, HP GC Auto Sampler Controller, Detector FID and Software-HP Chemstation. He gas was used as the carrier. The intra- and inter-assay CV were 1·6 % and 2·0 %, respectively.

Statistical analyses

All statistical analyses were performed using SPSS for Windows 11.5 (SPSS Inc., Chicago, IL, USA). Baseline characteristics are shown as means and standard deviations. All other data are shown as means with their standard errors. Fasting concentrations on the day subsequent to the consumption of foods enriched with and without 50 g carob fibre were compared by paired samples t test. Time series data for total and acylated ghrelin and serum leptin were shown as absolute values and normalized to baseline values, which was defined as time 0 min. Absolute responses to standardized bread were tested by a mixed linear model with subject as random factor and time, carob concentration and carob concentration ×  time as fixed factors. Statistical differences in the response of the blood parameters during the examinations were analysed using ANOVA. A probability P < 0·05 was considered as significant.

Pearson correlation coefficients were calculated for each subject between total and acylated plasma ghrelin and other biomarkers with and without placebo treatment. Individual coefficients of correlation were averaged and 5 % CI were calculated after correction with Fisher's z transformation.

Results

General characteristics and dietary intervention

The study population consisted of nine males and ten females. One subject had a BMI >26 kg/m2. None of the subjects showed a fasting glucose >6·1 mmol/l (Table 2). Total energy and nutrient intake at day 1 was similar in both treatments (Table 2).

Table 2 Baseline characteristics of participants*

(Mean values and standard deviations for nine males and ten females)

* For details of subjects and procedures, see Methods.

Colonic fermentation and SCFA

The day subsequent to the consumption of foods enriched with a total of 50 g carob fibre, fasting breath H concentrations were significantly higher than the day after consumption of control foods, indicating an enhanced colonic fermentation (57 (sem 9) v. 34 (sem 6) ppm; P = 0·032; Fig. 1), indicating good compliance of the participants. During the postprandial phase, breath H concentrations decreased rapidly (P = 0·001). Faecal concentrations of acetate, butyrate, proprionate and n-valerate as well as total SCFA were similar after carob fibre and control (data not shown).

Fig. 1 Postprandial breath H concentrations (cH2) after consumption of standardized bread on the day subsequent to the consumption of foods enriched with 50 g carob fibre (–▲–) or control (–○–) foods. cH2 were significantly higher after consumption of carob fibre compared with control (P < 0·001). For details of subjects and procedures, see Methods.

Fasting blood levels and postprandial response

Consumption of carob fibre the previous day did not significantly affect fasting plasma glucose, TAG and serum NEFA (Table 3), but resulted in higher plasma glucose (P = 0·029) and lower plasma TAG (P = 0·033) and serum NEFA (P < 0·001) responses after bread ingestion (Fig. 2). Fasting serum insulin and postprandial response of serum insulin to bread ingestion were similar after consumption of foods with or without carob fibre.

Table 3 Fasting blood concentrations of participants on the day subsequent to the consumption of foods enriched with 50 g carob fibre or control foods (day 2)*

(Mean values with their standard errors for nineteen participants)

* For details of subjects and procedures, see Methods.

Significance of paired samples t test is given. HOMA-IR, Homeostasis Model Assessment of Insulin Resistance.

Fig. 2 Postprandial response of plasma glucose, serum insulin, plasma TAG and serum NEFA after consumption of standardized bread on the day subsequent to the consumption of foods enriched with 50 g carob fibre (–●–) or control (–○–) foods. Carob fibre consumption resulted in higher plasma glucose (P = 0·029) and a lower plasma TAG (P = 0·033) and serum NEFA (P < 0·001). For details of subjects and procedures, see Methods.

Fasting acylated plasma ghrelin concentrations were increased on day 2, subsequent to the consumption of foods enriched with carob fibre, as compared with previous consumption of control (P = 0·046), while fasting total plasma ghrelin concentrations remained unchanged. Consumption of carob fibre also affected postprandial plasma ghrelin response (Fig. 3). Absolute total and acylated plasma ghrelin responses to bread ingestion were higher on the day subsequent to carob fibre consumption compared with control (P = 0·027 and P < 0·001, respectively). When plasma ghrelin concentrations were normalized to baseline, no effects of carob fibre consumption on changes of the total and acylated plasma ghrelin concentrations from baseline were observed, indicating that the magnitude of total and acylated plasma ghrelin response to the meal was not altered by carob fibre consumption.

Fig. 3 Postprandial absolute and relative response of total and acylated plasma ghrelin as well as serum leptin after consumption of standardized bread on the day subsequent to the consumption of foods enriched with 50 g carob fibre (–▲–) or control (–○–) foods. Carob fibre consumption resulted in higher absolute total and acylated plasma ghrelin (P = 0·027 and P < 0·001, respectively) but did not affect serum leptin concentrations. Differences in total and acylated plasma ghrelin and serum leptin from baseline were not affected by carob consumption. For details of subjects and procedures, see Methods.

Carob fibre consumption did not affect fasting serum leptin or absolute or relative postprandial serum leptin response after bread ingestion on day 2, compared with control (Fig. 3). However, when plasma leptin concentrations were normalized to baseline, a marginal increase in serum leptin levels after 150 min was observed (P = 0·070), indicating a slight change in the amplitude of serum leptin response.

Postprandial total and acylated plasma ghrelin were negatively correlated with plasma insulin and positively with NEFA (Table 4). Coefficients of correlations were higher when only postprandial responses on the day subsequent to the consumption of foods enriched with carob fibre were included. Coefficients of correlation were lower between total plasma ghrelin and other biomarkers.

Table 4 Pearson coefficients of correlation (PCC) between postprandial total and acylated plasma ghrelin and other biomarkers on the day subsequent to the consumption of foods enriched with carob fibre or control foods*

(Values are PCC and 95 % CI)

* For details of subjects and procedures, see Methods.

Correlations for both treatments are based on twenty-eight (fourteen time points, two treatments) and correlations for carob treatments are based on fourteen (fourteen time points, one treatment) pairs of data for plasma glucose, TAG and serum insulin, NEFA and leptin for each subject.

Discussion

The major findings of the present study were elevated total and acylated plasma ghrelin levels 24 h after carob fibre consumption, which are accompanied by an enhanced lipid metabolism. Carob fibre consumption also resulted in higher postprandial plasma glucose response.

We recently showed that acute administration of carob fibre lowered acylated ghrelin levels, increased RQ and energy expenditure with an acutely enhanced lipid metabolism and increased fat oxidation during a liquid meal challenge test28. The results of the present study show elevated ghrelin levels 24 h after carob consumption, suggesting that higher lipid utilization as observed after acute carob consumption induced a state comparable with a negative energy balance. In rats, acylated ghrelin not only promotes food intake but also decreases fat utilization and energy expenditure11, 29, 30. Ghrelin is also a suppressor of adipose tissue lipolysis via inhibition of AMP-activated protein kinase31, 32. In the present study, elevated ghrelin might have resulted in decreased circulating TAG and NEFA due to higher lipid utilization and suppressed lipolysis. The magnitude of postprandial serum NEFA suppression was similar between both treatments, suggesting a similar insulin-mediated NEFA suppression. However, NEFA slope after liver-mediated suppression was lower after carob consumption, suggesting a higher uptake of NEFA by muscle tissue. Beyond ghrelin, bioactive compounds such as polyphenols may also be responsible for these effects. Narenginin, a polyphenol found in grapefruit, has been shown to reduce plasma TAG in diabetic rats33 and inhibited apo-B secretion34. In rats, grape seed polyphenols also lowered plasma TAG, NEFA and apo-B35. A potential synergistic effect of dietary fibre and polyphenols might add to these effects. In rats, apple pectin combined with a polyphenol-rich apple concentrate reduced plasma cholesterol and TAG more effectively than pectin or polyphenols alone36.

Effects of elevated acylated ghrelin on long-term food intake after carob fibre consumption remain speculative due to the concomitant increase in total plasma ghrelin in the second half of postprandial response. The major isoform of ghrelin is desacyl ghrelin, which might counteract or abolish the effects of acylated ghrelin37.

In contrast with ghrelin, leptin acts to reduce food intake and increase energy expenditure by binding and activating its specific receptor in the hypothalamus10, 19, 38, 39. In vivo, leptin suppresses ghrelin release from isolated rat stomach40. Recently, it has been proposed that ghrelin secretion in human subjects is also regulated by leptin restraint12, 17. However, this hypothesis cannot be confirmed by the present study, as the effects were only marginal and 24-h profiles of leptin secretion are missing.

The increase in postprandial plasma glucose response after carob fibre consumption was an unexpected finding, since the consumption of a highly purified insoluble dietary fibre has been shown to improve insulin response directly after consumption and to enhance postprandial carbohydrate handling the subsequent day of ingestion41. This might be explained by the high content of polyphenols in carob fibre and the effect of polyphenols on glucose uptake. We recently showed that polyphenol-rich carob fibre, administered within a water–glucose solution, increased postprandial glucose and insulin responses, suggesting a deteriorated glycaemic control42. Cell studies have shown that polyphenols decrease glucose uptake into cells via inhibition of phosphatidylinositol 3-kinase, a key regulator of insulin-induced GLUT4 translocation43, 44. Our hypothesis is supported by the fact that serum insulin response was not altered by carob consumption despite higher plasma glucose response, suggesting that the effect is triggered by an alteration in insulin action rather than insulin secretion. However, other polyphenols activated phosphatidylinositol 3-kinase45; therefore, the mechanisms involved in the effect observed in the present study remain speculative.

In conclusion, an increase in total and acylated plasma ghrelin accompanied by enhanced lipid metabolism after carob fibre consumption suggests higher lipid utilization and suppressed lipolysis on the day subsequent to carob fibre consumption. However, elevated glucose levels also indicate potential adverse effects that might be caused by polyphenols and need to be addressed in future studies. Whether increased ghrelin concentrations after carob consumption exert unfavourable effects on energy homeostasis in human subjects needs to be addressed in middle and long-term studies.

Acknowledgements

We thank Andreas Wagner for his excellent technical assistance.

References

1Jenkins, DJ, Kendall, CW, Axelsen, M, Augustin, LS & Vuksan, V (2000) Viscous and non-viscous fibres, non-absorbable and low glycaemic index carbohydrates, blood lipids and coronary heart disease. Curr Opin Lipidol 11, 4956.
2Meyer, KA, Kushi, LH, Jacobs, DR Jr, Slavin, J, Sellers, TA & Folsom, AR (2000) Carbohydrates, dietary fiber, and incident type 2 diabetes in older women. Am J Clin Nutr 71, 921930.
3Schulze, MB, Liu, S, Rimm, EB, Manson, JE, Willett, WC & Hu, FB (2004) Glycemic index, glycemic load, and dietary fiber intake and incidence of type 2 diabetes in younger and middle-aged women. Am J Clin Nutr 80, 348356.
4Venter, CS, Vorster, HH & Cummings, JH (1990) Effects of dietary propionate on carbohydrate and lipid metabolism in healthy volunteers. Am J Gastroenterol 85, 549553.
5Thorburn, A, Muir, J & Proietto, J (1993) Carbohydrate fermentation decreases hepatic glucose output in healthy subjects. Metabolism 42, 780785.
6Kao, YH, Hiipakka, RA & Liao, S (2000) Modulation of endocrine systems and food intake by green tea epigallocatechin gallate. Endocrinology 141, 980987.
7Klaus, S, Pultz, S, Thone-Reineke, C & Wolfram, S (2005) Epigallocatechin gallate attenuates diet-induced obesity in mice by decreasing energy absorption and increasing fat oxidation. Int J Obes (Lond) 29, 615623.
8Gruendel, S, Garcia, AL, Otto, B, Mueller, C, Steiniger, J, Weickert, MO, Speth, M, Katz, N & Koebnick, C (2006) Carob pulp preparation rich in insoluble dietary fiber and polyphenols enhances lipid oxidation and lowers postprandial acylated ghrelin in humans. J Nutr 136, 15331538.
9Blaak, EE (2003) Fatty acid metabolism in obesity and type 2 diabetes mellitus. Proc Nutr Soc 62, 753760.
10Ahima, RS, Prabakaran, D, Mantzoros, C, Qu, D, Lowell, B, Maratos-Flier, E & Flier, JS (1996) Role of leptin in the neuroendocrine response to fasting. Nature 382, 250252.
11Tschop, M, Smiley, DL & Heiman, ML (2000) Ghrelin induces adiposity in rodents. Nature 407, 908913.
12Kalra, SP, Bagnasco, M, Otukonyong, EE, Dube, MG & Kalra, PS (2003) Rhythmic, reciprocal ghrelin and leptin signaling: new insight in the development of obesity. Regul Pept 111, 111.
13Kalra, SP & Kalra, PS (2003) Neuropeptide Y: a physiological orexigen modulated by the feedback action of ghrelin and leptin. Endocrine 22, 4956.
14Williams, J & Mobarhan, S (2003) A critical interaction: leptin and ghrelin. Nutr Rev 61, 391393.
15Gil-Campos, M, Aguilera, CM, Canete, R & Gil, A (2006) Ghrelin: a hormone regulating food intake and energy homeostasis. Br J Nutr 96, 201226.
16Korbonits, M, Goldstone, AP, Gueorguiev, M & Grossman, AB (2004) Ghrelin – a hormone with multiple functions. Front Neuroendocrinol 25, 2768.
17Kalra, SP, Ueno, N & Kalra, PS (2005) Stimulation of appetite by ghrelin is regulated by leptin restraint: peripheral and central sites of action. J Nutr 135, 13311335.
18Zhang, Y, Proenca, R, Maffei, M, Barone, M, Leopold, L & Friedman, JM (1994) Positional cloning of the mouse obese gene and its human homologue. Nature 372, 425432.
19Friedman, JM & Halaas, JL (1998) Leptin and the regulation of body weight in mammals. Nature 395, 763770.
20Bado, A, Levasseur, S, Attoub, S, et al. (1998) The stomach is a source of leptin. Nature 394, 790793.
21Sobhani, I, Bado, A, Vissuzaine, C, et al. (2000) Leptin secretion and leptin receptor in the human stomach. Gut 47, 178183.
22Federal Institute for Health Protection of Consumers and Veterinary Medicine (1999) The German Food Code and Nutrient Data Base (BLS II.3): Conception, Structure and Documentation of the Data Base blsdat. Berlin, Germany: BgVV Publications.
23Koebnick, C, Wagner, K, Thielecke, F, et al. (2005) An easy-to-use semi-quantitative food record validated for energy intake by using doubly labelled water technique. Eur J Clin Nutr 59, 989995.
24Owen, RW, Haubner, R, Hull, WE, Erben, G, Spiegelhalder, B, Bartsch, H & Haber, B (2003) Isolation and structure elucidation of the major individual polyphenols in carob fibre. Food Chem Toxicol 41, 17271738.
25Blom, WA, Stafleu, A, de Graaf, C, Kok, FJ, Schaafsma, G & Hendriks, HF (2005) Ghrelin response to carbohydrate-enriched breakfast is related to insulin. Am J Clin Nutr 81, 367375.
26Wu, Z, Bidlingmaier, M, Liu, C, De Souza, EB, Tschop, M, Morrison, KM & Strasburger, CJ (2002) Quantification of the soluble leptin receptor in human blood by ligand-mediated immunofunctional assay. J Clin Endocrinol Metab 87, 29312939.
27Friedewald, WT, Levy, RI & Fredrickson, DS (1972) Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 18, 499502.
28Dongowski, G, Lorenz, A & Proll, J (2002) The degree of methylation influences the degradation of pectin in the intestinal tract of rats and in vitro. J Nutr 132, 19351944.
29Inui, A (2001) Ghrelin: an orexigenic and somatotrophic signal from the stomach. Nat Rev Neurosci 2, 551560.
30Kojima, M & Kangawa, K (2002) Ghrelin, an orexigenic signaling molecule from the gastrointestinal tract. Curr Opin Pharmacol 2, 665668.
31Choi, K, Roh, SG, Hong, YH, Shrestha, YB, Hishikawa, D, Chen, C, Kojima, M, Kangawa, K & Sasaki, S (2003) The role of ghrelin and growth hormone secretagogues receptor on rat adipogenesis. Endocrinology 144, 754759.
32Kola, B, Hubina, E, Tucci, SA, et al. (2005) Cannabinoids and ghrelin have both central and peripheral metabolic and cardiac effects via AMP-activated protein kinase. J Biol Chem 280, 2519625201.
33Choi, JS, Yokozawa, T & Oura, H (1991) Improvement of hyperglycemia and hyperlipemia in streptozotocin-diabetic rats by a methanolic extract of Prunus davidiana stems and its main component, prunin. Planta Med 57, 208211.
34Borradaile, NM, Carroll, KK & Kurowska, EM (1999) Regulation of HepG2 cell apolipoprotein B metabolism by the citrus flavanones hesperetin and naringenin. Lipids 34, 591598.
35Del Bas, JM, Fernandez-Larrea, J, Blay, M, Ardevol, A, Salvado, MJ, Arola, L & Blade, C (2005) Grape seed procyanidins improve atherosclerotic risk index and induce liver CYP7A1 and SHP expression in healthy rats. Faseb J 19, 479481.
36Aprikian, O, Duclos, V, Guyot, S, Besson, C, Manach, C, Bernalier, A, Morand, C, Remesy, C & Demigne, C (2003) Apple pectin and a polyphenol-rich apple concentrate are more effective together than separately on cecal fermentations and plasma lipids in rats. J Nutr 133, 18601865.
37Asakawa, A, Inui, A, Fujimiya, M, Sakamaki, R, Shinfuku, N, Ueta, Y, Meguid, MM & Kasuga, M (2005) Stomach regulates energy balance via acylated ghrelin and desacyl ghrelin. Gut 54, 1824.
38Eriksson, J, Valle, T, Lindstrom, J, Haffner, S, Louheranta, A, Uusitupa, M & Tuomilehto, J (1999) Leptin concentrations and their relation to body fat distribution and weight loss – a prospective study in individuals with impaired glucose tolerance. DPS-study group. Horm Metab Res 31, 616619.
39Friedman, JM (2002) The function of leptin in nutrition, weight, and physiology. Nutr Rev 60, S1S14.
40Kamegai, J, Tamura, H, Shimizu, T, Ishii, S, Sugihara, H & Oikawa, S (2004) Effects of insulin, leptin, and glucagon on ghrelin secretion from isolated perfused rat stomach. Regul Pept 119, 7781.
41Weickert, MO, Mohlig, M, Koebnick, C, et al. (2005) Impact of cereal fibre on glucose-regulating factors. Diabetologia 48, 23432353.
42Gruendel, S, Otto, B, Garcia, AL, Wagner, K, Mueller, C, Weickert, MO, Heldwein, W, Speth, M, Katz, N & Koebnick, C (In the Press) Carob pulp preparation rich in insoluble dietary fibre and polyphenols triggers plasma glucose and serum insulin responses in combination with a glucose load in humans. Br J Nutr.
43Harmon, AW & Patel, YM (2004) Naringenin inhibits glucose uptake in MCF-7 breast cancer cells: a mechanism for impaired cellular proliferation. Breast Cancer Res Treat 85, 103110.
44Strobel, P, Allard, C, Perez-Acle, T, Calderon, R, Aldunate, R & Leighton, F (2005) Myricetin, quercetin and catechin-gallate inhibit glucose uptake in isolated rat adipocytes. Biochem J 386, 471478.
45Borradaile, NM, de Dreu, LE & Huff, MW (2003) Inhibition of net HepG2 cell apolipoprotein B secretion by the citrus flavonoid naringenin involves activation of phosphatidylinositol 3-kinase, independent of insulin receptor substrate-1 phosphorylation. Diabetes 52, 25542561.