The effect of acute hyperglycaemia on appetite and food intake in Type 1 diabetes mellitus

Antidiabetic, Antioxidant and Anti-Inflammatory Activities of Residual Aqueous Fraction of Ethulia conyzoides in Induced Type 2 Diabetic Rats

Oxidative stress and inflammation have been proven to be implicated in the pathogenesis of type 2 diabetes. Recent studies showed that Ethulia conyzoides had in-vitro antioxidant activity. This study investigated the in-vivo antidiabetic, antioxidant, and anti-inflammatory potential of the residual aqueous fraction of Ethulia conyzoides in type 2 diabetic-induced male Wistar rats. Sub-acute antidiabetic studies were done with varying doses (100, 200, and 400 mg/kg body weight) of residual aqueous fraction for 21 days. Blood glucose levels, serum insulin, and in vivo antioxidant and pro-inflammatory cytokines-tumour necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) -were measured at the end of the treatment. When rats were given different concentrations of residual aqueous fraction, there was a significant (p < 0.05) reduction in blood glucose, malondialdehyde (MDA), IL-1β, and TNF-α levels, as well as a significant (p < 0.05) increase in SOD (superoxide dismutase), catalase and insulin levels when compared to the diabetic control group. Furthermore, the 400 mg/kg body weight dosage concentration was found to be the most effective. This result suggests that the residual aqueous fraction of Ethulia conyzoides possesses significant antidiabetic, antioxidant and anti-inflammatory activities.

Comparison of appetite responses to high- and low-glycemic index postexercise meals under matched insulinemia and fiber in type 1 diabetes

BACKGROUND

Patients with type 1 diabetes face heightened risk of hypoglycemia after exercise. Subsequent overfeeding, as a preventative measure against hypoglycemia, negates the energy deficit after exercise. Patients are also required to reduce the insulin dose administered with postexercise foods to further combat hypoglycemia. However, the insulin dose is dictated solely by the carbohydrate content, even though postprandial glycemia is vastly influenced by glycemic index (GI). With a need to control the postexercise energy balance, appetite responses after meals differing in GI are of particular interest.

OBJECTIVES

We assessed the appetite response to low-glycemic index (LGI) and high-glycemic index (HGI) postexercise meals in type 1 diabetes patients. This assessment also offered us the opportunity to evaluate the influence of GI on appetite responses independently of insulinemia, which confounds findings in individuals without diabetes.

DESIGN

Ten physically active men with type 1 diabetes completed 2 trials in a randomized crossover design. After 45 min of treadmill exercise at 70% of the peak oxygen uptake, participants consumed an LGI (GI ∼37) or HGI (GI ∼92) meal with a matched macronutrient composition, negligible fiber content, and standardized insulin-dose administration. The postprandial appetite response was determined for 180 min postmeal. During this time, circulating glucose, insulin, glucagon, and glucagon-like peptide-1 (GLP-1) concentrations and subjective appetite ratings were determined.

RESULTS

The HGI meal produced an ∼60% greater postprandial glucose area under the curve (AUC) than did the LGI meal (P = 0.008). Insulin, glucagon, and GLP-1 did not significantly differ between trials (P > 0.05). The fullness AUC was ∼25% greater after the HGI meal than after the LGI meal (P < 0.001), whereas hunger sensations were ∼9% lower after the HGI meal than after the LGI meal (P = 0.001).

CONCLUSION

Under conditions of matched insulinemia and fiber, an HGI postexercise meal suppresses feelings of hunger and augments postprandial fullness sensations more so than an otherwise equivalent LGI meal in type 1 diabetes patients.

Initial evidence that GLP-1 receptor blockade fails to suppress postprandial satiety or promote food intake in humans

Glucagon-like peptide 1 (GLP-1) has incretin effects that are well-documented, but the independent role of GLP-1 action in human satiety perception is debated. We hypothesized that blockade of GLP-1 receptors would suppress postprandial satiety and increase voluntary food intake. After an overnight fast, eight normal weight participants (seven men, BMI 19-24.7 kg/m(2), age 19-29 year) were enrolled in a double-blind, placebo-controlled, randomized crossover study of the GLP-1 antagonist Exendin-[9-39] (Ex-9) to determine if the satiating effects of a meal are dependent on GLP-1 signaling in humans. Following a fasting blood draw, iv infusion of Ex-9 (600-750 pmol/kg/min) or saline began. Thirty minutes later, subjects consumed a standardized breakfast followed 90 min later (at the predicted time of maximal endogenous circulating GLP-1) by an ad libitum buffet meal to objectively measure satiety. Infusions ended once the buffet meal was complete. Visual analog scale ratings of hunger and fullness and serial assessments of plasma glucose, insulin, and GLP-1 concentrations were done throughout the experiment. Contrary to the hypothesis, during Ex-9 infusion subjects reported a greater decrease in hunger due to consumption of the breakfast (Ex-9 -62 ± 5; placebo -41 ± 9; P=0.01) than during placebo. There were no differences in ad libitum caloric intake between Ex-9 and placebo. Ex-9 increased glucose, insulin, and endogenous GLP-1, which may have counteracted any effects of Ex-9 infusion to block satiety signaling. Blockade of GLP-1 receptors failed to suppress subjective satiety following a standardized meal or increase voluntary food intake in healthy, normal-weight subjects.

Chlorophytum borivilianum root extract maintains near normal blood glucose, insulin and lipid profile levels and prevents oxidative stress in the pancreas of streptozotocin-induced adult male diabetic rats

The effect of C. borivilianum root on blood glucose, glycated hemoglobin (HbAIc), insulin and lipid profile levels in diabetes mellitus are not fully understood. This study therefore investigated the effect of C. borivilianum root on the above parameters and oxidative stress of the pancreas in diabetes.

METHODS

C. borivilianum root aqueous extract (250 and 500 mg/kg/day) was administered to streptozotocin (STZ)-induced male diabetic rats for 28 days. Body weight, blood glucose, HbA1c, insulin, lipid profile levels and glucose homeostasis indices were determined. Histopathological changes and oxidative stress parameters i.e. lipid peroxidation (LPO) and antioxidant enzymes activity levels of the pancreas were investigated.

RESULTS

C. borivilianum root extract treatment to diabetic rats maintained near normal body weight, blood glucose, HbA1c, lipid profile and insulin levels with higher HOMA-β cell functioning index, number of Islets/pancreas, number of β-cells/Islets however with lower HOMA-insulin resistance (IR) index as compared to non-treated diabetic rats. Negative correlations between serum insulin and blood glucose, HbA1c, triglyceride (TG) and total cholesterol (TC) levels were observed. C. borivilianum root extract administration prevented the increase in lipid peroxidation and the decrease in activity levels of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) with mild histopathological changes in the pancreas of diabetic rats.

CONCLUSIONS

C. borivilianum root maintains near normal levels of these metabolites and prevented oxidative stress-induced damage to the pancreas in diabetes.

The anorectic effect of GLP-1 in rats is nutrient dependent

GLP-1-induced insulin secretion from the β-cell is dependent upon glucose availability. The purpose of the current study was to determine whether CNS GLP-1 signaling is also glucose-dependent. We found that fasting blunted the ability of 3(rd) cerebroventricularly (i3vt)-administered GLP-1 to reduce food intake. However, fasted animals maintained the anorexic response to melanotan II, a melanocortin receptor agonist, indicating a specific effect of fasting on GLP-1 action. We also found that i3vt administration of leptin, which is also decreased with fasting, was not able to potentiate GLP-1 action in fasted animals. However, we did find that CNS glucose sensing is important in GLP-1 action. Specifically, we found that i3vt injection of 2DG, a drug that blocks cellular glucose utilization, and AICAR which activates AMPK, both blocked GLP-1-induced reductions in food intake. To examine the role of glucokinase, an important CNS glucose sensor, we studied glucokinase-heterozygous knockout mice, but found that they responded normally to peripherally administered GLP-1 and exendin-4. Interestingly, oral, but not i3vt or IP glucose potentiated GLP-1's anorectic action. Thus, CNS and peripheral fuel sensing are both important in GLP-1-induced reductions in food intake.

Effect of the once-daily human GLP-1 analogue liraglutide on appetite, energy intake, energy expenditure and gastric emptying in type 2 diabetes

AIMS

Liraglutide reduces bodyweight in patients with type 2 diabetes mellitus (T2DM). This study aimed to investigate the mechanisms underlying this effect.

METHODS

The comparative effects of liraglutide, glimepiride and placebo on energy intake, appetite, nausea, gastric emptying, antral distension, bodyweight, gastrointestinal hormones, fasting plasma glucose and resting energy expenditure (REE), were assessed in subjects with T2DM randomised to treatment A (liraglutide-placebo), B (placebo-glimepiride) or C (glimepiride-liraglutide). Assessments were performed at the end of each 4-week treatment period.

RESULTS

Energy intake was less (NS) with liraglutide vs placebo and glimepiride, and 24-h REE was higher (NS) with liraglutide vs placebo and glimepiride. Fasting hunger was less (p=0.01) with liraglutide vs placebo and glimepiride, and meal duration was shorter with liraglutide (p=0.002) vs placebo. Paracetamol AUC(0-60 min) and C(max) were less (p<0.01) and fasting peptide YY was lower (p ≤ 0.001) after liraglutide vs placebo and glimepiride. Bodyweight reductions of 1.3 and 2.0 kg were observed with liraglutide vs placebo and glimepiride (p<0.001). There were no differences on antral distension, nausea, or other gastro-intestinal hormones.

CONCLUSION

Liraglutide caused decreased gastric emptying and increased reduction in bodyweight. The mechanisms of the liraglutide-induced weight-loss may involve a combined effect on energy intake and energy expenditure.

Gastroparesis: pathogenesis, diagnosis and management

Gastroparesis is a prevalent condition that produces symptoms of delayed gastric emptying in the absence of physical blockage. The most common etiologies of gastroparesis are idiopathic, diabetic, and postsurgical disease, although some cases stem from autoimmune, paraneoplastic, neurologic or other conditions. Histologic examination of gastric tissues from patients with severe gastroparesis reveals heterogeneous and inconsistent defects in the morphology of enteric neurons, smooth muscle and interstitial cells of Cajal, and increased levels of inflammatory cells. Diagnosis is most commonly made by gastric emptying scintigraphy; however, wireless motility capsules and nonradioactive isotope breath tests have also been validated. A range of treatments have been used for gastroparesis including dietary modifications and nutritional supplements, gastric motor stimulatory or antiemetic medications, endoscopic or surgical procedures, and psychological interventions. Most treatments have not been subjected to controlled testing in patients with gastroparesis. The natural history of this condition is poorly understood. Active ongoing research is providing important insights into the pathogenesis, diagnosis, treatment and outcomes of this disease.

Hunger and thirst: issues in measurement and prediction of eating and drinking

Associations between hunger and eating and between thirst and drinking are generally weak. This stems, in part, from limitations in the measurement of these sensations which generally rely on temporal, motivational, metabolic and/or self-reported descriptive indices. Each is critically reviewed. Also problematic is the fact that the deterministic depletion-repletion concept of ingestive behavior fails to account for influences of a multitude of contravening cognitive, social, sensory and logistical factors. Although hunger and thirst serve some parallel purposes, sharp distinctions are also present with health implications. Of particular note are the observations that thirst ratings are higher and more stable over the day compared to hunger and thirst may be more motivating to drink than hunger is to eat. Coupling these observations with evidence that beverages have limited satiety value, they pose particular challenges and opportunities. Beverages can facilitate the delivery of nutrients to those desiring or requiring them, but also to those where they are not desired or required. The benefits and risks are a function of their use rather than their inherent properties.

Effects of peripheral administration of synthetic human glucose-dependent insulinotropic peptide (GIP) on energy expenditure and subjective appetite sensations in healthy normal weight subjects and obese patients with type 2 diabetes

BACKGROUND

Apart from their role in insulin secretion and glucose homeostasis, the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) exert a number of extra-pancreatic effects which in the case of GIP remain largely unknown.

DESIGN/PATIENTS

Six obese male patients with diet-controlled type 2 diabetes (T2DM) and six healthy lean male subjects were studied. The protocol included four experiments for each participant that were carried out in randomized order and included: GLP-1 infusion at a rate of 1 pmol/kg/min for 4 h, GIP at a rate of 2 pmol/kg/min, GLP-1 (at 1 pmol/kg/min) with GIP (at 2 pmol/kg/min), and placebo infusion for 4 h. Energy expenditure (EE) was measured throughout with indirect calorimetry and subjects were given a series of visual analogue scales to rate hourly their hunger, fullness, urge to eat and prospective consumption of food. Immediately following termination of the infusions all subjects were offered a free choice buffet lunch and total calorie and macronutrient intake was calculated.

RESULTS

During GIP infusion there was a trend for healthy subjects to report higher hunger scores and a reduction in EE only when compared with placebo. These parameters remained unchanged in patients with T2DM. Ad libitum energy intake after all four infusions was the same in both groups.

CONCLUSION

We report here for the first time that GIP infusion may impact on resting EE and subjective appetite sensations in normal weight healthy subjects and further studies with larger numbers of subjects are required to help define more conclusively the precise role of GIP in energy balance in humans.

Gastrointestinal symptoms and glycemic control in diabetes mellitus: a longitudinal population study

BACKGROUND

The prevalence of gastrointestinal (GI) symptoms is increased in diabetes, but their natural history is understood poorly and any impact of glycemic control is controversial. We aimed to quantify changes in GI symptom status and glycemic control among a population sample of patients with diabetes.

METHODS

Data on 10 chronic GI symptom complexes were obtained from a validated questionnaire at baseline and after 12 months. Changes in acute and chronic glycemic control were classified as always adequate, variable (deteriorated or improved), or always inadequate; acute glycemic control was assessed by fasting plasma glucose and chronic glycemic control by a validated self-report 5-point graded scale.

RESULTS

Baseline and follow-up data were available in 136 individuals with diabetes (mean age 59 years; 66% males; 95% type 2). The most prevalent GI symptom complexes were abdominal bloating/distension (35%), ulcer-like dyspepsia (35%), and irritable bowel syndrome (27%). Overall, between 7 and 24% reported a change in GI symptoms with the largest change in irritable bowel syndrome (24%), bloating/distension (22%), and ulcer-like dyspepsia (21%). Those who had a change in abdominal bloating (either loss or gain) over 12 months were more likely to have increased their mean fasting plasma glucose (P<0.05). Contrary to expectations, consistently poor self-reported glycemic control was only weakly associated with less persistent abdominal pain (r=-0.2, P=0.03), diarrhea (r=-0.22, P=0.01), and abdominal bloating (r=-0.2, P=0.03). Acute glycemic control was not significantly related to any GI symptoms.

CONCLUSION

We were unable to demonstrate any association between worsening GI symptoms and glycemic control.

Effect of duodenal glucose and acute hyperglycemia on rectal perception and compliance in response to tension-controlled rectal distension in healthy humans

BACKGROUND

Acute changes in blood glucose concentration affect gastrointestinal motor and sensory function. Tone and distensibility contribute to intact rectal function.

AIMS

To test the effects of duodenal glucose (euglycemic hyperinsulinemia), intravenous glucose (hyperglycemic hyperinsulinemia), and saline (euglycemic normoinsulinemia as control) on rectal perception and compliance in response to tension-controlled rectal distension.

METHODS

During duodenal glucose at 2 kcal min(-1), marked hyperglycemic clamp (approximately 13 mmol L(-1)), or saline as control, responses to fixed-tension rectal distension, applied by means of a computerized tensostat, were compared randomized on three separate days in eight healthy subjects.

RESULTS

At discomfort level (score 3 on the 0-4 rectal score scale), perception of rectal distension was significantly higher during euglycemic hyperinsulinemia (45 +/- 3 g cm(-2) tolerance) and significantly lower during hyperglycemia (83 +/- 4 g cm(-2) tolerance), both reaching significance versus control (64 +/- 6 g cm(-2) tolerance; P < 0.05). At this level, no relevant variations of rectal compliance were seen, which were 10.3 +/- 1 mL mmHg(-1) during duodenal glucose, 9.5 +/- 1 mL mmHg(-1) for the group with hyperglycemia, and 9.7 +/- 2 mL mmHg(-1) for the control.

CONCLUSION

Duodenal glucose provokes rectal hypersensitivity whereas acute hyperglycemia contributes to rectal hyposensitivity. Despite different rectal tenso-sensitivity, rectal compliance remains virtually unchanged. Any dysfunction may cause rectal complaints.

Relationships between human thirst, hunger, drinking, and feeding

There is a widely held view that hunger prompts feeding to ensure energy needs are met, while thirst cues drinking to address hydration requirements. However, recent changes in the nature of the food supply and eating patterns have raised questions about the functionality of these relationships with respect to maintaining energy balance. The increasing consumption of energy-yielding beverages and foods with diluted energy density, through the use of ingredients such as high-intensity sweeteners and fat replacers, poses new challenges to presumed homeostatic energy regulatory mechanisms. This review draws on findings from a recent observational study and other published evidence to explore whether shifts of food composition and use patterns may be disrupting relationships between thirst, hunger, drinking, and eating, resulting in positive energy balance (e.g., drinking low satiety, energy-yielding beverages in response to hunger). The observational study entailed collecting hourly appetitive ratings and dietary recalls from 50 adults for seven consecutive days. These data reveal a clear bimodal daily hunger pattern, whereas thirst is stronger and more stable throughout the day. Further, approximately 75% of fluid intake occurs peri-prandially, with the majority derived from energy-yielding beverages. While there is published evidence that drinking is responsive to feeding, support for the view that drinking is the more tightly regulated behavior is stronger. Our data indicates that, due to a number of plausible factors, neither absolute values nor changes of hunger or thirst are strong predictors of energy intake. However, it is proposed that stable, high thirst facilitates drinking, and with the increased availability and use of energy-yielding beverages that have low satiety properties, can promote positive energy balance. There are marked individual differences in mean daily hunger and thirst ratings with unknown implications for energy balance.

Modulation of food intake by glucose in patients with type 2 diabetes

OBJECTIVE

A gain in body weight is a common adverse effect of glucose-lowering therapies in patients with type 2 diabetes, the mechanisms of which are not completely understood. Blood glucose is considered to play a crucial role in the regulation of food intake. On this background, we hypothesized that a short-term reduction of blood glucose concentration to normal values acutely increases food intake in type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

To test this hypothesis, 12 patients with type 2 diabetes were examined twice, once during a euglycemic (5.0 mmol/l) clamp experiment and another time during a hyperglycemic (10.5 mmol/l) clamp. The experiments were performed in a single-blind fashion with the order of conditions balanced across patients. On both clamp conditions, insulin was infused at a constant rate of 2.5 mU/kg per min for 125 min. Simultaneously, a glucose solution was infused at a variable rate to achieve target glycemic levels. During the final 30 min of the clamps, the patients were allowed to eat as much as they liked from a standard breakfast buffet.

RESULTS

Compared with the hyperglycemic condition, the patients ingested on average 25 +/- 10% more energy during euglycemia (645 +/- 75 vs. 483 +/- 37 kcal; P = 0.029). The increased energy intake during euglycemia was equally distributed across macronutrient components, i.e., during euglycemia the patients ate more carbohydrates (+27.1 +/- 11.4%; P = 0.037), fat (+22.5 +/- 10.0%; P = 0.046), and proteins (+25.2 +/- 11.2%; P = 0.046) than during hyperglycemia. Circulating levels of insulin, amylin, leptin, ghrelin, and glucagon-like peptide-1 did not differ between the euglycemic and hyperglycemia clamp, excluding a major contribution of these hormones to the difference in food intake. Summing up the glucose administered intravenously and the food ingested yielded a remarkably similar total energy influx in both conditions (794 +/- 64 vs. 790 +/- 53 kcal; P = 0.961).

CONCLUSIONS

Together our data suggest that total energy supply to the organism is tightly regulated on a short-term basis independent of the route of influx. Alternatively, it can be hypothesized that euglycemia stimulated or that hyperglycemia suppressed food intake at the subsequent buffet meal in our type 2 diabetic patients. Regardless of these different interpretations, our data indicate an important regulatory role of glucose for food intake in type 2 diabetic patients that is of considerable clinical relevance.

Neuronal glucosensing: what do we know after 50 years?

Glucosensing neurons are specialized cells that use glucose as a signaling molecule to alter their action potential frequency in response to variations in ambient glucose levels. Glucokinase (GK) appears to be the primary regulator of most neuronal glucosensing, but other regulators almost certainly exist. Glucose-excited neurons increase their activity when glucose levels rise, and most use GK and an ATP-sensitive K(+) channel as the ultimate effector of glucose-induced signaling. Glucose-inhibited (GI) neurons increase their activity at low glucose levels. Although many use GK, it is unclear what the final pathway of GI neuronal glucosensing is. Glucosensing neurons are located in brain sites and respond to and integrate a variety of hormonal, metabolic, transmitter, and peptide signals involved in the regulation of energy homeostasis and other biological functions. Although it is still uncertain whether daily fluctuations in blood glucose play a specific regulatory role in these physiological functions, it is clear that large decreases in glucose availability stimulate food intake and counterregulatory responses that restore glucose levels to sustain cerebral function. Finally, glucosensing is altered in obesity and after recurrent bouts of hypoglycemia, and this altered sensing may contribute to the adverse outcomes of these conditions. Thus, although much is known, much remains to be learned about the physiological function of brain glucosensing neurons.

Energy intake and appetite are related to antral area in healthy young and older subjects

BACKGROUND

Gastric distension reduces food intake, and antral, rather than proximal, gastric distension may be the dominant mechanism in the induction of appetite-related sensations. Healthy aging is associated with reduced appetite.

OBJECTIVE

We examined the effects of different energy preloads on appetite, plasma cholecystokinin, antral area, and subsequent energy intake in healthy older and young subjects.

DESIGN

On 3 separate days, 12 young and 12 older subjects consumed 400 mL of a drink containing either 0 kcal (water), 250 kcal, or 750 kcal 70 min before a buffet-style meal.

RESULTS

Hunger was less in the older than in the young subjects (P < 0.001). Both nutrient preloads reduced hunger and increased fullness more than did water (P < 0.02), and older subjects were more full than were the young (P < 0.05). Antral area was greater after the nutrient preloads than after water (P = 0.001) and greater in the older than in the young subjects (P = 0.005). In both groups, food intake was suppressed in an energy-dependent manner (P = 0.008). Plasma cholecystokinin was greater in the older than in the young subjects (P = 0.003). Immediately before the meal, hunger (r = -0.59) and energy intake (r = -0.90) were inversely related and fullness (r = 0.66) was directly related to antral area (all: P < 0.001). Antral area, but not plasma cholecystokinin, was a predictor of subsequent energy intake.

CONCLUSION

In healthy young and older subjects, the suppression of subsequent energy intake by a liquid preload is nutrient dependent and comparable, and both satiation and satiety are related to antral area and (presumably) antral distension.