Gastric ghrelin, GOAT, leptin, and leptinR expression as well as peripheral serotonin are dysregulated in humans with obesity

BACKGROUND

Gastrointestinal hormone release and the regulation of appetite and body weight are thought to be dysbalanced in obesity. However, human data investigating the expression of gastrointestinal hormones in the obese are rare. We studied the expression of ghrelin, leptin, and the serotonergic system in stomach tissue and serum of obese and non-obese individuals.

METHODS

Gastric tissue and serum were collected from 29 adult obese (BMI 48.7 ± 10.6 kg/m(2) ; mean ± SD) who underwent laparoscopic sleeve gastrectomy. Gastric biopsies, surgery specimen or serum was obtained from 35 adult non-obese humans (BMI 22.7 ± 1.9 kg/m(2) ). Ghrelin, ghrelin O-acyl transferase (GOAT), leptin, leptin receptor, and tryptophan hydroxylase 1 (TPH1) mRNA expression were measured by qRT-PCR. Serotonin (5HT) and leptin protein concentration were quantified in tissue extracts and serum; GOAT and ghrelin-positive cells were immunohistologically quantified in tissue. Additionally, 21 blood immune markers were analyzed.

KEY RESULTS

In gastric tissue, GOAT-positive cells were reduced (p < 0.01), but ghrelin-positive cells and mRNA were increased (both p < 0.05) in obese compared with non-obese individuals. Gastric leptin (p < 0.001) and leptin receptor (p < 0.001) mRNA expression, as well as leptin concentrations in serum (p < 0.001), were increased in obese compared with non-obese individuals. Serum 5HT was reduced (p < 0.05), while tissue 5HT and TPH1 mRNA were reduced only by trend. Interleukin 1 receptor a (IL1Ra), IL-8, IL-12, and monocyte chemoattractant protein 1 (IL1Ra) were increased and IL1Ra correlated negatively with serum leptin.

CONCLUSIONS & INFERENCES

Our data indicate that obesity causes a dysregulation of gastrointestinal hormones at the tissue level and serum, including a negative correlation with an increased marker of subclinical inflammation.

Enhancement of synaptic strength in the somatosensory cortex following nerve injury does not parallel behavioural alterations

Following infraorbital nerve transection, underlying mechanisms of the altered synaptic strength were studied in rat barrel cortex slice experiments. In addition to the in vitro electrophysiological studies, open-field tests were run to detect possible behavioural changes associated with cortical oversensitization. Enhanced NMDA receptor-mediated component of the evoked field response appeared in the barrel cortex after nerve injury. The alteration was transient, very distinct on the first day following injury, and almost returned to normal level by the end of the second week. Behavioural changes had not followed this time-course since long-lasting alterations were detected in the open-field test. These observations are in agreement with findings that showed biphasic regenerative processes following nerve injuries in other cortical areas.

BGP-15, a hydroximic acid derivative, protects against cisplatin- or taxol-induced peripheral neuropathy in rats

The neuroprotective effect of BGP-15 against peripheral sensory neuropathy was studied in rats that were exposed to short-term cisplatin or taxol administration. The changes of nerve conduction velocity were determined in situ after treating the Wistar rats with BGP-15 (50, 100, and 200 mg/kg po daily doses throughout the experiment), cisplatin (1.5 mg/kg ip daily dose for 5 days), or taxol (5.0 mg/kg ip daily dose every other day in a 10-day interval) alone or giving the test compound in combination with cisplatin or taxol. Electrophysiological recordings were carried out in vivo by stimulating the sciatic nerve at both sciatic notch and ankle site. Neither motor nor sensory nerve conduction velocity was altered by any dose level of BGP-15 tested. Both anticancer drugs decreased the sensory nerve conduction velocity (SNCV). BGP-15 treatment prevented the impairment of SNCV either in part or totally in the cisplatin- or taxol-treated groups. This neuroprotective potential of BGP-15 could be well correlated with its recently described poly(ADP-ribose) polymerase- inhibitory effect and its ability to protect against the damages induced by the increased level of reactive oxygen species in response to anticancer treatment.

Discomfort: not pain but still unpleasant feelings from the gut

Most of the factors initiating food or fluid intake have already been studied, but much less is known about those terminating ingestion. We have hypothesised that discomfort originating from the gastrointestinal system may be one of those factors. Gut distension cause pain if the intestinal volume changes but merely discomfort if only the tension of the gut wall increases. It seems that mild unpleasantness (i.e. discomfort) arising from the gut as a result of moderate (quasi-isometric) distension, among and in concordance with other factors, may significantly reduce intake and hence contribute to physiological satiety. The arising discomfort can be detected by measuring the amount and rate of the ingestion, by recording and analysing ingestive behavior by taste-aversivity and taste-reactivity tests, etc. Conclusions of all experiments point to the same direction: tension increase in the gut wall causes discomfort and results in decrease of intake, i.e. satiety.

Conditioned taste aversion to gut distension in rats

The aim of this work was to study the negative effects of the intestinal stimulation by a method that is sensitive to assess internal malaise and discomfort. Effects of volumetric and "isometric" gut distension on the behavior were compared in the small and the large intestines, respectively. Chronically separated (Thiry-Vella) intestinal loops prepared from the upper jejunum and/or from the uppermost segment of the colon were stimulated with a rubber balloon. Conditioned taste aversion (CTA) series were accompanied with recording satiety and aversive behavioral indexes. Both isometric and volumetric stimuli elicited taste aversion. No essential differences between the two intestinal parts were found. Behavioral indices supported intake data: satiety indexes were similar to each other, whereas aversive indexes were high during stimulation and lower during testing. Data were consistent over conditions and time, proving the reliability of the method. Results are compared to earlier taste reactivity records.

Gender-related heart rate differences in human neonates

The aim of the present study was to examine gender-related differences in heart rate of human neonates controlled for their behavior. Previous studies could not find any difference in male and female fetuses and newborns, although this gender-dependent difference clearly exists in children and adults. The heart rate of 99 newborns (47 girls and 52 boys) was measured with simultaneous video recording of their behavior. Results proved that alert newborns showed the same difference as adults: boys had a significantly lower baseline heart rate than girls. This suggests that heart rate is gender-dependent from birth onward.

Modulation of taste reactivity by intestinal distension in rats

Discomfort created by intestinal distension may play a role in controlling intake behavior. We analyzed these effects in details by the taste reactivity test in Long-Evans rats. A balloon inserted into a separated Thiry-Vella intestinal loop was distended with different volumes of water (0.05, 0.09, 0.12, and 0.28 mL, respectively). Saccharin solution (0.001 M) was infused into the mouth via an implanted oral cannula nine times for 30 s, with 5-min intertrial intervals. The balloon was distended after the second and released following the seventh trial. Taste reactivity (TR) elements were videotaped and later analyzed for appetitive and aversive responses. The number of appetitive responses decreased after gut distension, whereas aversive elements were infrequent and stable. It is suggested that pleasantness of the taste stimulus decreased independently of the discomfort, which remained mild but steady; that is, sweet taste gradually lost its hedonic value but was not accompanied by an acquired aversion of the same taste. This finding may point to the difference of the motivational and discriminative effects of the internal stimuli.

Morphological and functional changes after benzalkonium chloride treatment of the small intestinal Thiry-Vella loop in rats

The aim of this work was to study the effects of benzalkonium chloride (BAC) treatment on the small intestine and its functioning in rats surgically prepared with Thiry-Vella intestinal loop. The loops were treated with either BAC, which ablated much of the myenteric plexus and extrinsic innervation, or with physiological saline (SAL). In vivo drinking experiments were performed to examine the effect on fluid intake and behavioral indices of distending the loop with a balloon. Spontaneous motility and its changes induced by acetylcholine (ACh) and histamine (His) were studied on isolated stripes in vitro. Finally, samples from the loops were examined histologically. Though reduction of the cell number was less than expected and no differences of the thickness of the muscular layer between the two groups was observed, BAC treatment altered the pattern of spontaneous activity and also the sensitivity to ACh and His in isolated stripes. In vivo distension of the SAL-treated loops reduced fluid intake and produced signs of aversivity; these effects were absent in the BAC-treated group. Our results show that despite the differences in the degree of ablation from those obtained by others, BAC treatment can be used to study the mechanisms underlying the effects of the enteral stimuli on the behavior.

Fluid intake and behavioral changes in rats associated with the distension of the small and large intestine

Effects of volumetric distension of the small and the large intestine on rats' behavior were compared. Rats were stimulated by a rubber balloon inserted into chronic isolated intestinal loops prepared from the lower duodenum-upper jejunum and from the upper colon in the same animal. Thresholds of 3 reaction classes (weak, strong, and painful) were not different from each other in the 2 loops. Distension decreased fluid intake in an intensity-dependent way, with weak and painful stimuli being less effective in the large intestine and strong stimuli less effective in the small bowel. Behavioral indexes supported intake data, satiety indexes were similar to each other and changed in time, whereas aversivity indexes differed in the 2 loops and as a function of intensity but not time. The author suggests that mild discomfort is a physiological satiety factor whereas strong and painful stimuli signal danger and induce aversivity.

Fluid intake and behavioral changes in rats associated with the distension of the small and large intestine

Effects of volumetric distension of the small and the large intestine on rats' behavior were compared. Rats were stimulated by a rubber balloon inserted into chronic isolated intestinal loops prepared from the lower duodenum-upper jejunum and from the upper colon in the same animal. Thresholds of 3 reaction classes (weak, strong, and painful) were not different from each other in the 2 loops. Distension decreased fluid intake in an intensity-dependent way, with weak and painful stimuli being less effective in the large intestine and strong stimuli less effective in the small bowel. Behavioral indexes supported intake data, satiety indexes were similar to each other and changed in time, whereas aversivity indexes differed in the 2 loops and as a function of intensity but not time. The author suggests that mild discomfort is a physiological satiety factor whereas strong and painful stimuli signal danger and induce aversivity.

A new method: double Thiry-Vella fistulas in rats to compare the effects of small and large intestinal stimulation on behaviour

A new method for comparing the effects of small and large intestinal mechanical stimulation was developed. Isolated intestinal loops were created by the Thiry-Vella method from the lower duodenal--upper jejunal, and from the upper colonic portion of the gut, respectively. This preparation allows parallel evaluation of stimulation effects and affects from both the small and the large intestine of the same animal. A balloon could be inserted into the isolated loops before each experimental session and removed afterward. Behavioral thresholds to changes in the volume of the gut were recorded and compared in the two loops. No essential differences between the two portions of the intestinal tract were detected by this method.

The effect of chronic alcohol treatment on the radial maze performance of rats

The effect of chronic alcohol drinking on maze behaviour was studied in laboratory rats. Thirteen animals received 20% alcohol for 15 weeks ad libitum, and 18 were kept under identical conditions drinking tap water. Both groups were then tested twice within one day for performance in an 8 arm radial maze after 48 h fluid deprivation. Reinforcing fluid droplets were placed at the end of each arm only at the beginning of the test. Total and erroneous entries to the arms, total time spent until reaching the criterion, and strategy of arm choice was recorded for each animal. Activity of the groups did not differ significantly, nor were differences in choosing strategy found. Alcoholic rats, however, showed a significant loss of performance in the second test: they frequently entered arms already visited, and in a number of cases were unable to complete the test within time. These and earlier findings suggest no impairment of learning ability or short term memory, but rather some kind of rigidity and invariability of behaviour.