Environmental life cycle assessment of production of the high intensity sweetener steviol glycosides from Stevia rebaudiana leaf grown in Europe: The SWEET project

PURPOSE

There is an increasing interest in the use of non-nutritive sweeteners to replace added sugar in food and beverage products for reasons of improving consumer health. Much work has been done to understand safety of sweeteners, but very little on sustainability. To address that gap, this study presents the results of a life cycle assessment (LCA) of production of rebaudioside A 60%, 95% pure (RA60) steviol glycoside mix from Stevia rebaudiana leaf grown in Europe.

METHODS

An attributional cradle-to-factory-gate life cycle assessment was conducted on growing of stevia leaves and extraction of steviol glycosides in Europe. Primary data were used from a case study supply chain. Results are reported in impact categories from the ReCiPe 2016 (H) method, with focus given to global warming potential, freshwater eutrophication, water consumption, and land use. Impacts are expressed both in terms of production mass and sweetness equivalence, a common metric for understanding high intensity sweetener potency. Sweetness equivalence of RA60 is typically 200 to 300 times that of sugar. Comparison of environmental impact is made to sugar (sucrose) produced from both cane and beets. The research is part of the EU project SWEET (sweeteners and sweetness enhancers: impact on health, obesity, safety, and sustainability).

RESULTS AND DISCUSSION

Global warming potential for production of RA60 was found to be 20.25 kgCO₂-eq/kg_RA60 on a mass basis and 0.081 kgCO₂-eq/kg_SE on a sweetness equivalence basis. Field production of stevia leaves was found to be the main source of impact for most impact categories, and for all four focus categories. Extraction of the RA60 was the main source of impact for the others. Leaf processing and seedling propagation were minor contributors to life cycle impact. Removal of international transport from the supply chain reduced global warming potential by 18.8%. Compared with sugar on a sweetness equivalence basis, RA60 has approximately 5.7% to 10.2% the impact for global warming potential, 5.6% to 7.2% the impact for land use, and is lower across most other impact categories.

CONCLUSION

This is the first LCA of steviol glycoside mix RA60 produced from leaf in Europe. The results indicate that RA60 can be used to reduce environmental impact of providing a sweet taste by replacing sugar across all impact categories. However, it is important to note that specific formulations in which RA60 is used will have a bearing on the final environmental impact of any food or beverage products. For solid foods, this requires further research.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11367-022-02127-9.

Learning in lockdown: Using the COVID-19 crisis to teach children about food and climate change

Food systems are significant sources of global greenhouse gas emissions (GHGE). Since emission intensity varies greatly between different foods, changing food choices towards those with lower GHGE could make an important contribution to mitigating climate change. Public engagement events offer an opportunity to communicate these multifaceted issues and raise awareness about the climate change impact of food choices. An interdisciplinary team of researchers was preparing food and climate change educational activities for summer 2020. However, the COVID-19 pandemic and lockdown disrupted these plans. In this paper, we report on shifting these events online over the month of June 2020. We discuss what we did and the reception to our online programme. We then reflect on and highlight issues that arose. These relate to: (1) the power dynamics of children, diet and climate change; (2) mental health, diet and COVID-19; (3) engaging the wider science, agriculture and food communities; (4) the benefits of being unfunded and the homemade nature of this programme; (5) the food system, STEAM (science, technology, engineering, arts and mathematics) and diversity; and (6) how our work fits into our ongoing journey of food and climate change education.

Systematic review of the evidence for sustained efficacy of dietary interventions for reducing appetite or energy intake

We assessed evidence for changes in efficacy of food-based interventions aimed at reducing appetite or energy intake (EI), and whether this could be used to provide guidance on trial design. A systematic search identified randomized controlled trials testing sustained efficacy of diets, foods, supplements or food ingredients on appetite and/or EI. Trials had to include sufficient exposure duration (≥3 days) with appetite and/or EI measured after both acute and repeated exposures. Twenty-six trials met the inclusion criteria and reported data allowing for assessment of the acute and chronic effects of interventions. Most (21/26) measured appetite outcomes and over half (14/26) had objective measures of EI. A significant acute effect of the intervention was retained in 10 of 12 trials for appetite outcomes, and six of nine studies for EI. Initial effects were most likely retained where these were more robust and studies adequately powered. Where the initial, acute effect was not statistically significant, a significant effect was later observed in only two of nine studies for appetite and none of five studies for EI. Maintenance of intervention effects on appetite or EI needs to be confirmed but seems likely where acute effects are robust and replicable in adequately powered studies.

The development and validation of the Addiction-like Eating Behaviour Scale

Background:

Overeating and obesity are frequently attributed to an addiction to food. However, there is currently a lack of evidence to support the idea that certain foods contain any specific addictive substance. An alternative approach is to focus on dimensions of observable behaviour, which may underpin a behavioural addiction to eating. To facilitate this, it is necessary to develop a tool to quantify addiction-like eating behaviour, which is not based on the clinical criteria for substance dependence. The current study provides initial validation of the Addiction-like Eating Behaviour Scale (AEBS).

Methods:

English speaking male and female participants (N=511) from a community sample completed the AEBS, alongside a range of other health- and eating-related questionnaires including the Yale Food Addiction Scale (YFAS) and Binge Eating Scale (BES). Participants also provided their height and weight to enable calculation of body mass index (BMI). Finally, to assess test–retest reliability, an additional 70 participants completed the AEBS twice, 2 weeks apart.

Results:

Principle components analysis revealed that a two-factor structure best accounted for the data. Factor 1 consisted of items that referred to appetitive drive, whereas factor two consisted of items that referred to dietary control practices. Both subscales demonstrated good internal reliability and test–retest reliability, and a confirmatory factor analysis confirmed the two-factor scale structure. AEBS scores correlated positively with body mass index (BMI) (P<0.001) and other self-report measures of overeating. Importantly, the AEBS significantly predicted variance in BMI above that accounted for by both the YFAS and BES (P=0.027).

Conclusions:

The AEBS provides a valid and reliable tool to quantify the behavioural features of a potential ‘eating addiction’. In doing so, the AEBS overcomes many limitations associated with applying substance-dependence criteria to eating.

EffectS of non-nutritive sWeetened beverages on appetITe during aCtive weigHt loss (SWITCH): Protocol for a randomized, controlled trial assessing the effects of non-nutritive sweetened beverages compared to water during a 12-week weight loss period and a follow up weight maintenance period

BACKGROUND

Acute and medium-term intervention studies suggest that non-nutritive sweeteners (NNS) are beneficial for weight loss, however there is limited human data on the long-term effects of consuming NNS on weight loss, maintenance, and appetite. Further research is therefore required to elucidate the prolonged impact of NNS consumption on these outcome measures.

METHODS/DESIGN

A randomized parallel groups design will be used to assess whether regular NNS beverage intake is equivalent to a water control in promoting weight loss over 12-weeks (weekly weight loss sessions; Phase I), then supporting weight maintenance over 40-weeks (monthly sessions; Phase II) and subsequently independent weight maintenance over 52-weeks (Phase III) in 432 participants. A subset of these participants (n=116) will complete laboratory-based appetite probe days (15 sessions; 3 sessions each at baseline, at the start of phase I and the end of each phase). A separate subset (n=50) will complete body composition scans (DXA) at baseline and at the end of each phase. All participants will regularly be weighed and will complete questionnaires and cognitive tasks to assess changes in body weight and appetitive behaviours. Measures of physical activity and biochemical markers will also be taken.

DISCUSSION

The trial will assess the efficacy of NNS beverages compared to water during a behavioural weight loss and maintenance programme. We aim to understand whether the impact of NNS on weight, dietary adherence and well-being are beneficial or transient and effects on prolonged successful weight loss and weight maintenance through sustained changes in appetite and eating behaviour.

TRIAL REGISTRATION

Clinical Trials: NCT02591134; registered: 23.10.2015.

Coconut and sunflower oil ratios in ice cream influence subsequent food selection and intake

The effect of coconut oil (CO, containing mainly medium chain triglycerides - MCTs) and sunflower oil (SO, containing mainly long chain triglycerides - LCTs) used as fat source (10% fat ice cream) in different ratios (25% CO and 75% SO - 25CO:75SO, 50% CO and 50% SO - 50CO:50SO, 75% CO and 25% SO - 75CO:25SO) was investigated to assess differences in appetite and ad-libitum (evening and snack) food intake using a single blind design. 36 healthy female participants consumed a fixed portion (150g) of ice cream 45min before an ad-libitum dinner and snacks. Appetite sensations were tracked across the day. Participants ate significantly less fat after 75CO:25SO than 25CO:75SO (p=0.007) and there was also a trend for lower fat intake in this condition as compared to 50CO:50SO (p=0.068). High fat savoury snack intake significantly decreased after 75CO:25SO in comparison with both 25CO:75SO (p=0.038) and 50CO:50SO (p=0.008). Calorie intake from snacks was also found to be significantly lower after 25CO:75SO and 50CO:50SO than 75CO:25SO (p=0.021 and 0.030 respectively). There was no effect of condition on appetite or desire ratings over the day. Eating a standard portion of ice cream containing different ratios of MCTs and LCTs can modestly influence acute food selection and intake, with MCTs manifesting their effect earlier and LCTs later due to differences in the absorption and metabolism of these lipids. However, the differences evident in the present study were small, and require further research before firm conclusions can be drawn.

Will smaller plates lead to smaller waists? A systematic review and meta-analysis of the effect that experimental manipulation of dishware size has on energy consumption

It has been suggested that providing consumers with smaller dishware may prove an effective way of helping people eat less and preventing weight gain, but experimental evidence supporting this has been mixed. The objective of the present work was to examine the current evidence base for whether experimentally manipulated differences in dishware size influence food consumption. We systematically reviewed studies that experimentally manipulated the dishware size participants served themselves at a meal with and measured subsequent food intake. We used inverse variance meta-analysis, calculating the standardized mean difference (SMD) in food intake between smaller and larger dishware size conditions. Nine experiments from eight publications were eligible for inclusion. The majority of experiments found no significance difference in food intake when participants ate from smaller vs. larger dishware. With all available data included, analysis indicated a marginal effect of dishware size on food intake, with larger dishware size associated with greater intake. However, this effect was small and there was a large amount of heterogeneity across studies (SMD: -0.18, 95% confidence interval: -0.35, 0.00, I(2) = 77%). Evidence to date does not show that dishware size has a consistent effect on food intake, so recommendations surrounding the use of smaller plates/dishware to improve public health may be premature.

Plasma obestatin and autonomic function are altered in orexin-deficient narcolepsy, but ghrelin is unchanged

Narcolepsy-cataplexy is characterised by orexin deficiency, sleep disturbance, obesity and dysautonomia. Ghrelin and obestatin affect both energy intake and sleep. Our aim was to investigate ghrelin, obestatin and metabolic/autonomic function in narcolepsy-cataplexy. Eight narcolepsy-cataplexy patients (seven CSF orexin-deficient) and eight matched controls were studied. The subjects had a fixed energy meal with serial blood samples and measurement of heart rate variability (HRV). Fasting plasma obestatin was more than threefold higher in narcolepsy subjects (narcolepsy 89.6 ± 16 pg/ml vs. control 24.9 ± 3 pg/ml, p < 0.001). There was no change in HRV total power, but post-prandial low-frequency (LF) power and high-frequency (HF) power were lower in the narcolepsy group [area under the curve (AUC): HF power narcolepsy 1.4 × 10(5) ± 0.2 × 10(5) vs. control 3.3 × 10(5) ± 0.6 × 10(5 )ms(2)/h, p < 0.001]. On multiple regression analyses, the only significant predictor of plasma obestatin was HF power, which was inversely correlated with obestatin (β = -0.65 R (2) = 38 %, p = 0.009). Fasting and post-prandial plasma ghrelin were similar in both groups (narcolepsy 589.5 ± 88 pg/ml vs. control 686.9 ± 81 pg/ml, p = 0.5; post-prandial AUC-narcolepsy 161.3 ± 22 ng/ml/min vs. control 188.6 ± 62 ng/ml/min, p = 0.4). Only the narcolepsy group had significant suppression of plasma ghrelin after the meal (ANOVA, p = 0.004). In orexin-deficient narcolepsy, fasting plasma ghrelin is unaltered, and post-prandial suppression is preserved. Fasting plasma obestatin is increased and correlates with autonomic dysfunction. As obestatin affects NREM sleep, we suggest that increased plasma levels contribute to the disrupted sleep-state control in narcolepsy.

Acute effects of a herb extract formulation and inulin fibre on appetite, energy intake and food choice

The impact of two commercially available products, a patented herb extract Yerbe Maté, Guarana and Damiana (YGD) formulation and an inulin-based soluble fermentable fibre (SFF), alone or in combination, on appetite and food intake were studied for the first time in a double blind, placebo-controlled, cross-over design. 58 normal to slightly overweight women consumed a fixed-load breakfast followed 4h later by an ad libitum lunch. They were administered YGD (3 tablets) and SFF (5g in 100ml water), YGD and water (100ml), SFF and placebo (3 tablets) or water and placebo 15min before meals. Appetite was assessed using visual analogue scales, and energy intake was measured at lunch. Significant reductions in food intake and energy intake were observed when YGD was present (59.5g, 16.3%; 112.4kcal, 17.3%) and when SFF was present (31.9g, 9.1%; 80kcal, 11.7%) compared with conditions were products were absent. The lowest intake (gram and kcal) was in the YGD+SFF condition. Significant reductions in AUC hunger and AUC desire to eat were also observed after YGD+SFF combination. The data demonstrate that YGD produces a robust short-term effect on caloric intake, an effect augmented by SFF. Caloric compensation for SFF indicates independent effects on appetite regulation.

Ghrelin does not orchestrate the metabolic changes seen in fasting but has significant effects on lipid mobilisation and substrate utilisation

OBJECTIVE

Short-term fasting is associated with increased GH pulsatility and mobilisation of fats, but underlying mechanisms are unclear. We studied ghrelin's role during fasting and the effects of exogenous ghrelin on lipid mobilisation.

DESIGN

Randomised placebo-controlled study.

METHODS

In this study, ten controls (body mass index (BMI) 23.3±3.2), ten morbidly obese subjects (BMI 50.1±10.6) and six post-gastrectomy subjects (BMI 25.2±1.0) were fasted for 36  h undergoing regular blood sampling. On a separate occasion, subjects were infused with either i.v. ghrelin (5  pmol/kg per min) or saline over 270  min.

RESULTS

Obese and post-gastrectomy subjects had lower ghrelin compared with controls (ANOVA, P=0.02) during the fast. Controls and gastrectomy subjects showed a similar increase in GH pulsatility, circulating non-esterified fatty acids (NEFA) and 3β-hydroxybutyrate (3 HB). Obese subjects had an impaired GH response (P<0.001), reduced excursions of 3 HB (P=0.01) but no change in NEFA excursions (P=0.09) compared with controls. Ghrelin infusion increased GH, NEFA and ketone bodies (ANOVA, P<0.0001) in all the three groups, but GH response was impaired in the obese subjects (P=0.001). Ghrelin also induced a significant (ANOVA, P=0.004) biphasic NEFA response to meals in all the subjects.

CONCLUSIONS

Despite low circulating ghrelin, gastrectomy subjects maintain a normal metabolic response to fasting, implying that ghrelin plays a minimal role. In contrast, infused ghrelin has significant effects on lipid mobilisation and induces a marked biphasic NEFA response to meals. Hence, ghrelin may play a significant role in meal-related substrate utilisation and metabolic flexibility.

Ghrelin inhibits autonomic function in healthy controls, but has no effect on obese and vagotomized subjects

OBJECTIVE

Ghrelin inhibits sympathetic nervous system (SNS) activity in rodents. We studied the effect of ghrelin on healthy humans, in obesity and in vagotomized subjects.

DESIGN

Randomized, double-blinded, placebo-controlled crossover.

SUBJECTS

Seven lean [mean body mass index (BMI) 23·6 ± 0·9 kg/m(2) ], seven morbidly obese (mean BMI 50·9 ± 4·4 kg/m(2) ) and seven post-gastrectomy subjects (mean BMI 22·0 ± 1·1 kg/m(2) ).

MEASUREMENTS

Subjects were randomized to intravenous ghrelin (5 pmol/kg/min) or saline over 270 min. Subjects had a fixed calorie meal and a free choice buffet during the infusion. Heart rate variability (HRV) was measured. Total power (TP) represents overall autonomic function, low-frequency (LF) power represents sympathetic and parasympathetic activity, and high-frequency (HF) power represents parasympathetic activity. Very low (VLO) frequency represents the frequency band associated with thermogenesis.

RESULTS

Preliminary anova analysis, looking at all three subject groups together, showed that ghrelin had an overall highly significant inhibitory effect on TP (P = 0·001), HF power (P = 0·04), VLO power (P = 0·03) and no effect on LF (P = 0·07). Further subset analysis revealed that ghrelin had a significant effect on TP (P = 0·03), borderline effect on LF power (P = 0·06) and no effect on HF power (P = 0·1) in healthy controls. By contrast in obese subjects, ghrelin had no effect on TP (P = 0·3), LF (P = 0·5) and HF (P = 0·06) and also no effect in the vagotomized subjects on TP (P = 0·7), LF (P = 0·7) and HF (P = 0·9). Ghrelin had no effect on the LF/HF ratio.

CONCLUSIONS

Ghrelin inhibits SNS activity in healthy controls with a moderate effect on parasympathetic nervous system activity but had no effect on obese subjects. Vagotomized subjects also did not respond to ghrelin, suggesting the vagus nerve is important for the effects of peripheral ghrelin on the SNS.

Acute effects of olanzapine on behavioural expression including the behavioural satiety sequence in female rats

Olanzapine is a novel antipsychotic drug known to induce clinically significant weight gain. Although the cause of such weight gain is not fully known, drug-induced changes in appetite and food intake are likely to play a significant role together with other possible mechanisms enhancing weight and/or adiposity. We assessed acute drug effects on 1 hour intake and behavioural expression in female rats. Low doses of olanzapine (0.5 and 1 mg/kg) enhanced acute mash intake. Marked drug effects were seen on a number of behaviours following olanzapine over a range of doses. These effects included dose-related reductions in activity and exploratory behaviours and associated substantial dose-related increases in resting behaviour. Behavioural data were also used to plot drug effects over time, including behavioural satiety sequence (BSS) profiles, to evaluate whether olanzapine's hyperphagic effects might be a consequence of altered satiety development. BSS profiles reflected enhanced eating behaviour at low doses (0.5 and 1 mg/kg) but showed dose-related increases in resting, indicative of drug-induced sedation, which meant that it was impossible to fully discern olanzapine's effects on satiety. Acute olanzapine induces both hyperphagia and sedation, both of which may promote weight gain and adiposity, but which interact competitively.

The effects of sibutramine on the microstructure of eating behaviour and energy expenditure in obese women

Given the suggestion that many potential anti-obesity drugs may enhance within-meal satiation, few studies have directly measured the effects of any drug on the microstructure of human eating behaviour. The effects of 7 days dosing with sibutramine 10 mg and 15 mg a day on appetite and energy balance were determined in 30 obese women (BMI 34.6 +/- 3.3 kg/m2, age 46.0 +/- 12.9 years) using a Universal Eating Monitor (UEM) and indirect calorimetry, in a double-blind, placebo-controlled crossover study. At day 7, sibutramine 10 mg and 15 mg reduced food intake by 16.6% and 22.3%, respectively (p < 0.001), compared with placebo. Sibutramine reduced eating rate compared with placebo rather than meal length (10 mg p < 0.05; 15 mg p < 0.001). In addition, sibutramine 10 mg significantly reduced hunger later in the meal (p < 0.05) and sibutramine 15 mg increased fullness early in the meal (p < 0.01), both of which are consistent with enhanced within-meal satiation. Sibutramine had little effect on resting metabolic rate, although 15 mg did significantly reduce respiratory quotient at several time points during the test day. These results provide novel evidence that decreased consumption of a test meal induced by sibutramine is primarily because of reduced eating rate, enhancing the deceleration in cumulative food intake within a meal associated with the development of satiety. Changes in within-meal appetite ratings appear particularly sensitive to drug-induced enhancement of satiation, and may provide key indices for assessing the therapeutic potential of novel anti-obesity drugs.

Chronic clozapine treatment in female rats does not induce weight gain or metabolic abnormalities but enhances adiposity: implications for animal models of antipsychotic-induced weight gain

The ability of clozapine to induce weight gain in female rats was investigated in three studies with progressively lowered doses of clozapine. In an initial preliminary high dose study, clozapine at 6 and 12 mg/kg (i.p., b.i.d.) was found to induce weight loss. In a subsequent intermediate dose study, we obtained no evidence for clozapine-induced weight gain despite using identical procedures and doses of clozapine (1-4 mg/kg, i.p., b.i.d.) with which we have observed olanzapine-induced weight gain, hyperphagia, enhanced adiposity and metabolic changes [Cooper G, Pickavance L, Wilding J, Halford J, Goudie A (2005). A parametric analysis of olanzapine-induced weight gain in female rats. Psychopharmacology; 181: 80-89.]. Instead, clozapine induced weight loss without alteration in food intake and muscle mass or changes in levels of glucose, insulin, leptin and prolactin. However, these intermediate doses of clozapine enhanced visceral adiposity and elevated levels of adiponectin. In a final study, low doses of clozapine (0.25-0.5 mg/kg, i.p, b.i.d.) induced weight loss. These data demonstrate that clozapine-induced weight gain can be much more difficult to observe in female rats than olanzapine-induced weight gain. Moreover, these findings contrast with clinical findings with clozapine, which induces substantial weight gain in humans. Clozapine-induced enhanced adiposity appears to be easier to observe in rats than weight gain. These findings, along with other preclinical studies, suggest that enhanced adiposity can be observed in the absence of antipsychotic-induced weight gain and hyperphagia, possibly reflecting a direct drug effect on adipocyte function independent of drug-induced hyperphagia [e.g. Minet-Ringuet J, Even P, Valet P, Carpene C, Visentin V, Prevot D, Daviaud D, Quignard-Boulange A, Tome D, de Beaurepaire R (2007). Alterations of lipid metabolism and gene expression in rat adipocytes during chronic olanzapine treatment. Molecular Psychiatry; 12: 562-571.]. These and other findings which show that the results of studies of antipsychotic treatment in animals do not always mimic clinical findings have important implications for the use of animal models of antipsychotic-induced weight gain. With regard to weight gain the results obtained appear to depend critically on the experimental procedures used and the specific drugs studied. Thus such models are not without limitations. However, they do consistently demonstrate the ability of various antipsychotics to enhance adiposity.

Effects of olanzapine in male rats: enhanced adiposity in the absence of hyperphagia, weight gain or metabolic abnormalities

Many of olanzapine's (OLZ) actions in humans related to weight regulation can be modelled in female rats (Cooper et al., 2005). Such effects include weight gain, hyperphagia, enhanced visceral adiposity and elevated Levels of insulin and adiponectin. As sex differences have been reported in the effects of antipsychotic drugs, including OLZ, in rats, the current study extended our study in female rats by directly comparing the actions of OLZ in maLes using identical methodology. Individually housed male Han Wistar rats were administered OLZ twice daily (i.p.), at 0, 1, 2, and 4 mg/kg over 21 days. Both differences from, and simiLarities to, the data obtained in females were obtained. Males treated with OLZ showed reduced weight gain, enhanced visceral adiposity and reduced lean muscle mass. There were no accompanying changes in food or water intake. OLZ did not induce changes in plasma levels of insulin, leptin or glucose. Significant elevation of adiponectin was observed. OLZ-treated males displayed elevated prolactin and suppressed testosterone. OLZ's effects in humans can very clearly be most validly modelled in female rats, although the cause(s) of the sex difference in OLZ's actions in rats are not clear. However, the finding that significantly enhanced adiposity is seen in both male and female rats, in other animal species (mice and dogs) and in humans suggests that studies in male rats of OLZ's effects may be of value, by highlighting the consistent ability of OLZ to increase visceral adiposity. It is hypothesized that such adiposity is a key, clinically relevant, common component of OLZ's actions which may be, at Least partially, independent of both OLZinduced weight gain and hyperphagia, and which is induced reliably in male and female rats and other animal species. Possible mechanisms involved in the effects reported are discussed.

Metformin prolongs the postprandial fall in plasma ghrelin concentrations in type 2 diabetes

BACKGROUND

Weight loss is difficult to achieve in type 2 diabetes and many therapies are associated with weight gain, an effect attenuated by metformin. We studied the effects of metformin on energy expenditure, appetite and the regulation of PYY and ghrelin in type 2 diabetes.

METHODS

Plasma peptide YY (PYY), ghrelin, resting metabolic rate (RMR), postprandial thermogenesis (PPTG), and appetite ratings were measured at baseline and following a mixed meal in 11 type 2 diabetic subjects treated with diet alone (T2D) and 10 treated with metformin monotherapy (T2MF). The groups were similar in age, gender and adiposity.

RESULTS

There were no differences in baseline anthropometric, or metabolic variables between the groups. Postprandially, plasma ghrelin fell equally in both groups (23% versus 24.5%, p < 0.05 versus baseline, p = NS between groups) but were reduced for longer in T2MF (below baseline 60-240 min T2MF versus 60-180 min T2D) coincidentally with a prolonged sensation of fullness and suppression of hunger in the metformin-treated group. There were no differences in PYY concentrations, RMR or PPTG.

CONCLUSIONS

Metformin prolongs the postprandial fall in ghrelin concentrations. These effects may prolong the inter-meal interval, thereby decreasing snack intake and daily energy intake, promoting weight loss.

Therapeutic potential of targeting the endocannabinoids: implications for the treatment of obesity, metabolic syndrome, drug abuse and smoking cessation

Rimonabant (SR141716, Acomplia) has been described as an antagonist/inverse agonist at the cannabinoid receptor type 1 (CB1). It has been widely used as a tool to evaluate the mechanisms by which cannabinoid agonists produce their pharmacological effects and to elucidate the respective physiological or pathophysiological roles of the CB1 receptor. It has become increasingly clear that rimonabant can exert its own intrinsic actions. These may be viewed as evidence of either the inverse agonist nature of rimonabant or of tonic activity of the endocannabinoid system. To date, data obtained from clinical trials (RIO North America, RIO Europe and RIO Lipid) indicate that rimonabant may have clinical benefits in relation to its anti-obesity properties and as a novel candidate for the treatment of metabolic and cardiovascular disorders associated with overweight and obesity. Other clinical trials, such as the STRATUS study, have also shown that rimonabant may be effective in smoking cessation, and that the drug has a reasonable safety profile. Recently, it has been shown that rimonabant prevents indomethacin-induced intestinal injury by decreasing the levels of pro-inflammatory cytokine tumour necrosis factor alpha (TNFalpha), thus indicating that CB1 receptor antagonists might exhibit potential anti-inflammatory activity in acute and chronic diseases.

Antipsychotic-induced weight gain

Novel 'atypical' antipsychotic drugs represent a substantial improvement on older 'typical' drugs. However, clinical experience has shown that some, but not all, of these drugs can induce substantial weight gain. This interferes with compliance with drug taking and has expected effects on morbidity and mortality. In this review, we summarize current thinking on: (i) the extent to which different 'atypical' drugs induce weight gain; (ii) the possible roles of various neurotransmitters and neuropeptides in this adverse drug reaction; and (iii) the state of development of animal models in this area. We also outline major areas for future research.

Anorexia and weight loss in male rats 24 h following single dose treatment with orexin-1 receptor antagonist SB-334867

Acute systemic treatment with the selective orexin-1 receptor antagonist SB-334867 (30 mg/kg, i.p.) has been reported not only to inhibit food intake and to accelerate behavioural satiety in rats, but also to produce a significant loss of bodyweight over the 24 h period post-dosing. The present studies were designed to test the hypothesis that the inhibition of weight gain following acute treatment with SB-334867 is due to a persistent anorectic action of the compound. In Experiment 1, the acute effects of SB-334867 (30 mg/kg, i.p.) on food intake and behaviour in a 1 h test with palatable mash were assessed as a function of injection-test interval. Results confirmed that, when administered 30 min prior to testing, SB-334867 significantly suppressed mash intake and accelerated behavioural satiety. More importantly, significant anorexia and behavioural change were also observed when animals were tested 24 h, but not 48 h, post-dosing. As previously reported, all animals treated with the orexin-1 receptor antagonist lost bodyweight over the 24 h period following acute treatment. The generality of these findings was confirmed in Experiment 2, where acute treatment with SB-334867 (30 mg/kg, i.p.) significantly suppressed home cage chow consumption over the 24 h period post-dosing, an effect also accompanied by a significant loss of bodyweight. The results of Experiment 3 showed that, following i.p. administration of 30 mg/kg, SB-334867 has good CNS penetration, reaches peak plasma and brain concentrations at 30 min, and maintains good exposure over 4 h post-dosing. Overall, current data support the hypothesis that a persistent anorectic action contributes to the significant loss of bodyweight observed 24 h following acute dosing with SB-334867. As the compound is virtually undetectable in plasma or brain beyond 8 h post-dosing, and since nothing is known about potentially active metabolites, we consider the possibility that single dose treatment with SB-334867 results in enduring alterations to the orexin-1 receptor and/or downstream signalling pathways.

A parametric analysis of olanzapine-induced weight gain in female rats

RATIONALE

Some novel antipsychotics, including olanzapine, induce weight gain and metabolic abnormalities, which represent the major adverse effects of these drugs. However, the mechanism(s) involved in such effects are unclear.

OBJECTIVE

The aim of this study was to develop, in female rats, a parametric model of olanzapine-induced weight gain and metabolic abnormalities and evaluate it against clinical findings.

METHODS

Female rats were administered olanzapine b.i.d. at doses of 0, 1, 2 and 4 mg/kg over 20 days, and a wide range of variables were recorded during and after drug administration.

RESULTS

Olanzapine increased both 24 h and total food intake. This was associated with rapid onset weight gain and increased adiposity (assessed by visceral fat pad masses). Insulin, but not glucose, concentrations were elevated, with a significant increase in the HOMA-IR index, indicative of insulin resistance. A nonsignificant trend towards higher levels of leptin was observed. Paradoxically, there was a significant increase in adiponectin. All of these variables showed maximal increases at either 1 or 2 mg/kg and attenuated effects at 4 mg/kg. Prolactin levels were also increased by olanzapine. However, for this variable, there was a clear dose-response curve, with the maximal effect at the highest dose (4 mg/kg).

CONCLUSIONS

These data suggest that aspects of olanzapine-induced weight gain and metabolic abnormalities can possibly be modelled in female rats. It is suggested that olanzapine-induced hyperphagia acts as an initial stimulus which leads to weight gain, enhanced visceral adiposity and subsequent insulin resistance, although the latter may be ameliorated by compensatory responses in adiponectin levels. Prolactin elevation appears likely not to be involved in the weight gain, adiposity and metabolic changes seen in this model.

Satiety enhancement by selective orexin-1 receptor antagonist SB-334867: influence of test context and profile comparison with CCK-8S

Acute systemic treatment with the selective orexin-1 (OX1R) antagonist SB-334867 reduces food intake in rats, an effect associated with an acceleration in behavioural satiety and unrelated to gross behavioural disruption, alterations in palatability, or toxicity. However, as enhanced satiety is behaviourally indexed by an earlier-than-normal transition from eating to resting, and since orexin-A has been implicated in mechanisms of arousal, it remains possible that sedation contributes to the anorectic effect of acute OX1R blockade. Previous work has shown that, when treated with SB-334867 (30 mg/kg, i.p.) 30 min before a 1h test with palatable food, rats begin to show appreciable levels of resting 10-15 min earlier than under control conditions (i.e. around 20 min versus 30-35 min into the session). The present results demonstrate that a 20 min increase in the injection-test interval (i.e. 50 min) had no significant impact on the anorectic, behavioural or weight gain effects of SB-334867 in non-deprived male rats. Most importantly, this altered treatment regimen led to a temporal profile of resting virtually identical to that previously observed with the more conventional 30 min injection-test interval. Although parallel studies indicated that the OX1R antagonist accelerated the onset of resting (and suppressed most active behaviours) even in the absence of food, an equianorectic dose of the natural satiety-related signal cholescystokinin octapeptide (CCK-8S; 5 microg/kg, i.p.) also produced very similar behavioural effects regardless of the presence of food. Together with evidence that SB-334867 preserves the structural integrity of natural feeding behaviour, does not induce nausea/illness or alter taste/palatability and fails to influence EEG measures of arousal/sleep, the present findings are consistent with the view that acute OX1R antagonism selectively enhances satiety. However, unlike the immediate short-circuiting of the satiety sequence induced by CCK-8S, the slower response to SB-334867 implies a more indirect mechanism of action.

Differential effects of the selective orexin-1 receptor antagonist SB-334867 and lithium chloride on the behavioural satiety sequence in rats

Recent studies have shown that acute systemic administration of the selective orexin-1 receptor antagonist SB-334867 significantly reduces food intake in rats. Although this anorectic action of orexin-1 receptor blockade is associated with an acceleration in the transition from eating to resting, it is widely recognised that the behavioural indices of satiety are not dissimilar to those of illness. In this context, Experiment 1 confirmed a significant anorectic effect of 90 (but not 60) mg/kg lithium chloride (LiCl) in male rats presented with palatable mash in the home-cage environment. Experiment 2 employed a continuous monitoring technique to contrast the effects of LiCl (90 mg/kg) and SB-334867 (10 and 30 mg/kg) on food intake and behaviour during a 1-h test with palatable mash. SB-334867 dose-dependently inhibited food intake, with the higher dose producing a comparable degree of appetite suppression (approximately 40%) to that seen with LiCl. Despite equivalent anorectic action, the two compounds produced very different effects on behaviour. LiCl reduced active behaviours (locomotion, rearing, grooming and sniffing), slowed the rate of eating and disrupted the behavioural satiety sequence (BSS). In contrast, SB-334867 (30 mg/kg) decreased the duration of feeding and grooming, and modestly accelerated the transition between eating and resting. Furthermore, whereas LiCl failed to alter posttreatment bodyweight gain, SB-334867 (30 mg/kg) produced a significant weight loss in the 24-h period immediately following injection. Overall, the divergent profiles obtained with equianorectic doses of LiCl and SB-334867 provide convincing evidence for the behavioural selectivity of SB-334867-induced anorexia.

Palatability, food intake and the behavioural satiety sequence in male rats

Food intake is influenced not only by nutritional status but also by diverse environmental factors. Indeed, a unique quality of food reward is its strong modulation by palatability cues, such as taste, with animals generally preferring diets that are sweet and avoiding those that are either bitter or sour. As appetite suppressants (including those currently in development) could alter food intake by modifying taste sensitivity and/or palatability, the aim of the present study was to characterise the influence of taste adulteration on the normal structure of feeding behaviour, i.e., the behavioural satiety sequence (BSS). Adult male rats were initially habituated both to the basic test diet (mash) and the test arena. Following stabilisation of basal intake, a continuous monitoring technique was used to profile behaviour in weekly 1-h sessions during which the animals were presented, in counterbalanced order, with the basic diet (control) or one of four taste-adulterated variants (0.015% quinine, 0.04% quinine, 0.2% saccharin, 0.3% saccharin). Food intake was strongly suppressed by the higher quinine concentration but was not significantly altered by any of the other additives. Behavioural analysis revealed that this anorectic-like response to 0.04% quinine-adulterated food was associated with a significant reduction in the peak feeding response, highly atypical intermittent food sampling/digging and the virtual absence of resting behaviour. Importantly, this pattern of behavioural change is readily distinguishable from those seen in response to other manipulations that reduce intake, including selective anorectics, sedatives and psychostimulants. Despite the lack of significant effect on food intake or the duration of feeding behaviour, dietary adulteration with 0.015% quinine (and, to a lesser degree, 0.3% saccharin) produced some effects on behavioural structure/time course consistent with a mild aversive response, i.e., bouts of midsession food sampling and a delay in the transition from eating to resting. Data are discussed in relation to the specific behavioural signature to quinine-induced anorexia and its potential utility in identifying appetite suppressants that may modify intake via changes in taste sensitivity and/or palatability.

Effects of systematic variation in presatiation and fasting on the behavioural satiety sequence in male rats

Preclinical research on the neurobiology of appetite regulation is increasingly employing detailed behavioural assessment in addition to measures of food intake. One of the most widely used approaches examines treatment effects on the behavioural satiety sequence (BSS), a concept describing the predictable pattern of behavioural change (feeding-->grooming-->resting) associated with the process of satiation in rats, mice and other mammals. Surprisingly, however, comparatively little published detail is available concerning the impact of more natural appetite modulators on the BSS. In two separate experiments, a continuous monitoring technique was used to calibrate the effects of prefeeding (3, 6 and 9 min) and prior fasting (3, 6 and 12 h) on the microstructure of rat behaviour during a 1 h test with palatable mash. Prefeeding significantly increased eating latencies and reduced both food intake and total duration (but not frequency) of feeding behaviour. The reduction in time spent eating was most evident during the first 15 min of the test when feeding is normally at peak levels. Although behavioural structure was fully preserved in all test conditions, the two larger preloads resulted in shifts to the left (i.e., an acceleration) in the BSS. In contrast, fasting for 6 and 12 h (but not 3 h) increased food intake and duration (but not frequency) of feeding behaviour in the early part of the test. All fasting conditions (including 3 h) produced considerable shifts to the right (i.e., a delay) in the BSS, confirming the greater sensitivity of this measure relative to food intake per se. The potential utility of these reference profiles is discussed in relation to drug-induced changes in food intake and the BSS.

Orexins and appetite regulation

Initial research on the functional significance of two novel hypothalamic neuropeptides, orexin-A and orexin-B, suggested an important role in appetite regulation. Since then, however, these peptides have also been shown to influence a wide range of other physiological and behavioural processes. In this paper, we review the now quite extensive literature on orexins and appetite control, and consider their additional effects within this context. Although the evidence for orexin (particularly orexin-A and the orexin-1 receptor) involvement in many aspects of ingestive physiology and behaviour is incontrovertible, central administration of orexins is also associated with increased EEG arousal and wakefulness, locomotor activity and grooming, sympathetic and HPA activity, and pain thresholds. Since the orexin system is selectively activated by signals indicating severe nutritional depletion, it would be highly adaptive for a hungry animal not only to seek sustenance but also to remain fully alert to dangers in the environment. Crucial evidence indicates that orexin-A increases food intake by delaying the onset of a behaviourally normal satiety sequence. In contrast, a selective orexin-1 receptor antagonist (SB-334867) suppresses food intake and advances the onset of a normal satiety sequence. These data suggest that orexin-1 receptors mediate the episodic signalling of satiety and appear to bridge the transition from eating to resting in the rats' feeding-sleep cycle. The argument is developed that the diverse physiological and behavioural effects of orexins can best be understood in terms of an integrated set of reactions which function to rectify nutritional status without compromising personal survival. Indeed, many of the non-ingestive effects of orexin administration are identical to the cluster of active defences mediated via the lateral and dorsolateral columns of the midbrain periaqueductal gray matter, i.e., somatomotor activation, vigilance, tachycardia, hypertension and non-opioid analgesia. In our view, therefore, the LH orexin system is very well placed to orchestrate the diverse subsystems involved in foraging under potentially dangerous circumstances, i.e., finding and ingesting food without oneself becoming a meal for someone else.