The role of enterostatin and apolipoprotein AIV on the control of food intake

Circulating Apolipoprotein A-IV presurgical levels are associated with improvement in insulin sensitivity after Roux-en-Y gastric bypass surgery

BACKGROUND

Apolipoprotein A-IV (ApoA-IV) has been shown to be involved in obesity and diabetes pathogenesis in animal studies, but its role in humans is uncertain.

OBJECTIVES

The objective of this study was to determine the relation of ApoA-IV with changes in glucose metabolism and weight after bariatric surgery.

SETTING

University Hospital.

METHODS

The patients (n = 49) included lean controls (n = 8) and patients before and after a mean of 7 months after laparoscopic adjustable gastric banding (LAGB, n = 12), laparoscopic Roux-en-Y gastric bypass (RYGB, n = 22), or laparoscopic sleeve gastrectomy (SG, n = 11). ApoA-IV and other hormone assays were performed in the fasting and the postprandial state. Pearson's correlation analyses controlled for baseline BMI and percent excess weight loss (EWL) were used to determine relationships between ApoA-IV levels and insulin resistance (HOMA-IR).

RESULTS

With all bariatric procedures combined, the change in ApoA-IV [533 versus 518 microg/L, P = .813] or ApoA-IV area under the curve (AUC - 1072 versus 1042, P = .939) was not significant. None of the surgeries individually affected levels of fasting or ApoA-IV AUC. Bariatric surgery resulted in a decrease in HOMA-IR (5.3 versus 2.0, P<.001). In the RYGB group, higher baseline ApoA-IV levels correlated with decrease in HOMA-IR [r = -.6, P = .008]. This relationship was independent of EWL and was not observed in the LAGB or SG group. There was no association of ApoA-IV levels with EWL, insulin secretion, Peptide-YY, or leptin levels.

CONCLUSION

Preoperative ApoA-IV levels, rather than changes in levels, positively correlate with improvements in insulin sensitivity independent of weight loss after RYGB.

Stimulation of Apolipoprotein A-IV expression in Caco-2/TC7 enterocytes and reduction of triglyceride formation in 3T3-L1 adipocytes by potential anti-obesity Chinese herbal medicines

BACKGROUND

Chinese medicine has been proposed as a novel strategy for the prevention of metabolic disorders such as obesity. The present study tested 17 Chinese medicinal herbs were tested for their potential anti-obesity effects.

METHODS

The herbs were evaluated in terms of their abilities to stimulate the transcription of Apolipoprotein A-IV (ApoA-IV) in cultured Caco-2/TC7 enterocytes. The herbs that showed stimulating effects on ApoA-IV transcription were further evaluated in terms of their abilities to reduce the formation of triglyceride in differentiated 3T3-L1 adipocytes.

RESULTS

ApoA-IV transcription was stimulated by Rhizoma Alismatis and Radix Angelica Sinensis in a dose- and time-dependent manner in cultured Caco-2/TC7 cells. Moreover, these two herbs reduced the amount of triglyceride in differentiated 3T3-L1 adipocytes.

CONCLUSION

The results suggest that Rhizoma Alistmatis and Radix Angelica Sinensis may have potential anti-obesity effects as they stimulate ApoA-IV transcription and reduce triglyceride formation.

Diurnal changes in intestinal apolipoprotein A-IV and its relation to food intake and corticosterone in rats

To further investigate the role of intestinal aplipoprotein A-IV (apo A-IV) in the management of daily food intake, we examined the diurnal patterns in apo A-IV gene and protein expression in freely feeding (FF) and food-restricted (FR; food provided 4 h daily for 4 wk) rats that were killed at 3-h intervals throughout the 24-h diurnal cycle. In FF rats, the intestinal apo A-IV mRNA and protein levels showed a circadian rhythm concomitant with the feeding pattern. The daily pattern of fluctuation of apo A-IV, however, was altered in FR rats, which had a marked increase in intestinal apo A-IV levels during the 4-h feeding period of light phase. In both FF and FR rats, increased plasma corticosterone (Cort) levels temporally coincided with the increasing phase of intestinal apo A-IV mRNA and protein expression. Depletion of Cort by adrenalectomy abolished the diurnal rhythm by decreasing the apo A-IV expression during the dark period but did not change the feeding rhythm. Exposure of adrenalectomized rats to consistent Cort level (50-mg continuous release Cort pellet) resulted in fixed apo A-IV levels throughout the day. These results indicate that intestinal apo A-IV exhibits a diurnal rhythm, which can be regulated by endogenous Cort independently of the light-dark cue. The fact that intestinal apo A-IV levels were consistent with the food intake during the normal diurnal cycle as well as during the cycle of 4-h feeding each day suggests that intestinal apo A-IV is involved in the regulation of daily food intake.

Diurnal rhythm of apolipoprotein A-IV in rat hypothalamus and its relation to food intake and corticosterone

Apolipoprotein A-IV (apo A-IV) is a satiety protein synthesized in the small intestine and hypothalamus. To further understand the roles of central apo A-IV in the management of daily food intake, we have examined the diurnal patterns of hypothalamic apo A-IV gene and protein expression in freely feeding and food-restricted (food provided 4 h daily between 1000 h and 1400 h) rats. In freely feeding rats, the hypothalamic apo A-IV mRNA and protein levels fluctuated, with high levels during the light phase, peaking at 0900 h (3 h after lights on), and low levels during the dark phase, with a nadir at 2100 h (3 h after lights off). The daily patterns of the fluctuation, however, were altered in food-restricted rats, which had a marked decrease in hypothalamic apo A-IV mRNA and protein levels during the 4 h-feeding period of the light phase. Although corticosterone (CORT) secretion temporally coincided with the decreasing phase of apo A-IV in the hypothalamus, depletion of CORT by adrenalectomy significantly decreased, rather than increased, hypothalamic apo A-IV mRNA and protein levels. These results indicate that the diurnal expression of hypothalamic apo A-IV is regulated by factors other than the circulating CORT, for example, the reduced food intake and body weight in adrenalectomized animals. The fact that hypothalamic apo A-IV level and food intake were inversely related during the normal diurnal cycle as well as in the period of restricted feeding suggests that hypothalamic apo A-IV is involved in the regulation of daily food intake.

Further evidence for the association between obesity-related traits and the apolipoprotein A-IV gene

OBJECTIVE

To investigate associations and gene-environment interactions of APOA-IV gene polymorphisms with obesity-related phenotypes in a Brazilian population.

METHODS

A total of 391 individuals (171 men and 220 women) were genotyped for Xbal, Thr347Ser and Gln360His polymorphisms by PCR-RFLP methods. Adjusted body mass index (BMI) and waist circumference (WC) were compared among genotypes/haplotypes by unpaired t-test or analysis of variance. Gene-environment interactions were tested by analysis of variance using a general linear model.

RESULTS

Analysis of the APOA-IV gene variants separately showed that X*2 and 347Ser alleles were associated with higher BMI (P=0.02 for both polymorphisms). Haplotype analysis confirmed this association. For these polymorphisms, the effect on BMI appeared to depend on smoking status (test for interaction, P=0.007 and 0.02, respectively), the Thr347Ser variant was associated with a BMI increase in smokers only (P=0.002). At the single-locus level no association was observed between 360His allele and BMI; however, haplotype analyses showed an association of this gene variant and higher BMI. A trend for association with WC (P=0.05) was observed in male carriers of the 360His allele. The effect of this polymorphism also depended on smoking status (test for interaction, P=0.018). Nonsmoker male carriers of the 360His allele had a larger waist circumference than homozygotes for the Gln allele (P=0.003).

CONCLUSION

Our data suggest that the APOA-IV gene polymorphisms investigated are associated with obesity-related traits. The effects of X*2 and 347Ser variants on BMI and the 360His variant on waist circumference depended on smoking status.

Food intake in rats is unaffected by the profile of dietary essential fatty acids

Food intake may be differentially responsive to the type of fat in the diet. The present investigation sought to evaluate the energy intake of rats maintained on either a low-fat or a high-fat diet mixed with an oil rich in either linoleic (18:2; n-6; safflower oil) or linolenic (18:3; n-3; flaxseed oil) acid. In Experiment 1, rats (n=28) consumed low-fat versions of either the safflower oil diet or the flaxseed oil diet, each at 9.28% fat (wt/wt). In Experiment 2, different rats (n=28) consumed high-fat versions of these diets, each at 23.6% fat (wt/wt). Within each experiment, the energy intake of rats receiving the safflower oil diet was compared to the energy intake of rats receiving the flaxseed oil diet. Food intake was measured under short-term, long-term and food-deprived conditions. In Experiment 1, short-term energy intakes were not different between the groups, thus demonstrating equal acceptance of the test diets. There were no consistent differences in long-term energy intakes between the safflower group and the flaxseed group. In addition, there were no differences in energy intake under the food-deprivation condition. Results from Experiment 2 paralleled those of Experiment 1. Taken together, the present results suggest that the essential fatty acid profile of the maintenance diet does not influence food intake when nutritive oils are the predominant fatty acid source.

Peripheral signals conveying metabolic information to the brain: short-term and long-term regulation of food intake and energy homeostasis

Numerous peripheral signals contribute to the regulation of food intake and energy homeostasis. Mechano- and chemoreceptors signaling the presence and energy density of food in the gastrointestinal (GI) tract contribute to satiety in the immediate postprandial period. Changes in circulating glucose concentrations appear to elicit meal initiation and termination by regulating activity of specific hypothalamic neurons that respond to glucose. Other nutrients (e.g., amino acids and fatty acids) and GI peptide hormones, most notably cholecystokinin, are also involved in short-term regulation of food intake. However, the energy density of food and short-term hormonal signals by themselves are insufficient to produce sustained changes in energy balance and body adiposity. Rather, these signals interact with long-term regulators (i.e., insulin, leptin, and possibly the orexigenic gastric peptide, ghrelin) to maintain energy homeostasis. Insulin and leptin are transported into the brain where they modulate expression of hypothalamic neuropeptides known to regulate feeding behavior and body weight. Circulating insulin and leptin concentrations are proportional to body fat content; however, their secretion and circulating levels are also influenced by recent energy intake and dietary macronutrient content. Insulin and leptin concentrations decrease during fasting and energy-restricted diets, independent of body fat changes, ensuring that feeding is triggered before body energy stores become depleted. Dietary fat and fructose do not stimulate insulin secretion and leptin production. Therefore, attenuated production of insulin and leptin could lead to increased energy intake and contribute to weight gain and obesity during long-term consumption of diets high in fat and/or fructose. Transcription of the leptin gene and leptin secretion are regulated by insulin-mediated increases of glucose utilization and appear to require aerobic metabolism of glucose beyond pyruvate. Other adipocyte-derived hormones and proteins that regulate adipocyte metabolism, including acylation stimulating protein, adiponectin, diacylglycerol acyltransferase, and perilipin, are likely to have significant roles in energy homeostasis.