Alloxan-induced glucoprivic feeding deficits are blocked by D-glucose and amygdalin

The Effect of Amygdalin on Endoplasmic Reticulum (ER) Stress Induced Hepatic Steatosis in Mice

Background

Endoplasmic reticulum (ER) stress creates abnormalities in the insulin action, inflammatory responses, lipoprotein B100 degradation, and hepatic lipogenesis. Hepatic steatosis leads to a broad spectrum of hepatic disorders such as nonalcoholic fatty liver disease (NAFLD) and NASH. Amygdalin has beneficial effects on asthma, bronchitis, diabetes, and atherosclerosis. We designed this study to evaluate the effect of amygdalin on the ER stress induced hepatic steatosis.

Methods

Inbred mice received saline, DMSO and amygdalin, as control groups. ER stress was induced by tunicamycin (TM) injection. Amygdalin was administered 1 h before the TM challenge (Amy + TM group). Mice body and liver weights were measured. Hematoxylin and eosin (H&E) and oil red O staining from liver tissue, were performed. Alanin aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride and cholesterol levels were measured.

Results

Histological evaluation revealed that amygdalin was unable to decrease the TM induced liver steatosis; however, ALT and AST levels decreased [ALT: 35.33(2.15) U/L versus 92.33(6.66) U/L; (57.000, (50.63, 63.36), P < 0.001) and AST: 93(5.09) U/L versus 345(97.3) U/L, (252, (163.37, 340.62), P < 0.001)]. Amygdalin also decreased triglyceride and cholesterol plasma levels in the Amy + TM group [TG: 42.66(2.15) versus 53.33(7.24) mg/dL; (10.67, (3.80, 17.54), P = 0.006) and TC: 9.33(3.55) versus 112.66(4.31) mg/dL, (103.33, (98.25, 108.40) P < 0.001)].

Conclusion

Amygdalin improved the ALT, AST, and lipid serum levels after the TM challenge; however, it could not attenuate hepatic steatosis.

Hindbrain catecholamine neurons control multiple glucoregulatory responses

Reduced brain glucose availability evokes an integrated constellation of responses that protect and restore the brain's glucose supply. These include increased food intake, adrenal medullary secretion, corticosterone secretion and suppression of estrous cycles. Our research has focused on mechanisms and neural circuitry underlying these systemic glucoregulatory responses. Using microinjection techniques, we found that localized glucoprivation of hindbrain but not hypothalamic sites, elicited key glucoregulatory responses, indicating that glucoreceptor cells controlling these responses are located in the hindbrain. Selective destruction of hindbrain catecholamine neurons using the retrogradely transported immunotoxin, anti-dopamine beta-hydroxylase conjugated to saporin (DSAP), revealed that spinally-projecting epinephrine (E) or norepinephrine (NE) neurons are required for the adrenal medullary response to glucoprivation, while E/NE neurons with hypothalamic projections are required for feeding, corticosterone and reproductive responses. We also found that E/NE neurons are required for both consummatory and appetitive phases of glucoprivic feeding, suggesting that multilevel collateral projections of these neurons coordinate various components of the behavioral response. Epinephrine or NE neurons co-expressing neuropeptide Y (NPY) may be the neuronal phenotype required for glucoprivic feeding: they increase NPY mRNA expression in response to glucoprivation and are nearly eliminated by DSAP injections that abolish glucoprivic feeding. In contrast, lesion of arcuate nucleus NPY neurons, using the toxin, NPY-saporin, does not impair glucoprivic feeding or hyperglycemic responses. Thus, hindbrain E/NE neurons orchestrate multiple concurrent glucoregulatory responses. Specific catecholamine phenotypes may mediate the individual components of the overall response. Glucoreceptive control of these neurons resides within the hindbrain.

Genetic variance contributes to ingestive processes: a survey of 2-deoxy-D-glucose-induced feeding in eleven inbred mouse strains

The feeding response following administration of the anti-metabolic glucose analogue, 2-deoxy-d-glucose (2DG), is conceptualized as an experimental model of glucoprivation, which may contribute to the understanding of inter-individual differences in glucose and carbohydrate intake and, ultimately, obesity. Although variation in the intake of several nutrients as well as food and water are known to be associated with genetic variation, it is not known whether 2DG-induced feeding is similarly genotype dependent. The present study therefore examined 2DG-induced feeding in mice of 11 inbred (A/J, AKR/J, BALB/cJ, CBA/J, C3H/HeJ, C57BL6/J, C57BL10/J, DBA/2J, SJL/J, SWR/J, 129P3/J) and one outbred (CD-1) strains across a wide range of previously determined effective 2-DG doses (200, 400, 600, 800 mg/kg) and test times (1-4 h). Orderly dose-dependent increases in 2DG-induced feeding occurred after all four doses in outbred CD-1 and inbred DBA/2J mice, across the three highest doses for BALB/cJ, SJL/J and 129P3/J mice, and across the two highest doses for CBA/J and AKR/J mice. Limited instances of 2DG-induced feeding were noted only at the highest dose in A/J and C3H/HeJ mice, or at a moderate dose in C57BL/6J mice. Further, the full 2DG dose range failed to alter food intake in C57BL/10J mice, and produced significant reductions in food intake in SWR/J mice. Food intake after 2DG doses of 200-600 mg/kg, but not 800 mg/kg, displayed significant cross-correlation, suggesting that large 2DG doses may recruit non-specific effects upon food intake. There was no correlation between food intake in the absence (vehicle baseline) of and presence of 2DG, suggesting that the regulation of glucose intake in non-challenged mice does not predict subsequent responses to glucoprivic challenge. The data demonstrate genotype-dependent variability in this glucoprivic response, and may provide the basis for the subsequent identification of trait-relevant genes.

Third ventricular alloxan reversibly impairs glucose counterregulatory responses

Glucokinase (GK) is hypothesized to be the critical glucosensor of pancreatic beta-cells and hypothalamic glucosensing neurons. To understand the role of GK in glucoprivic counterregulatory responses, we injected alloxan, a GK inhibitor and toxin, into the third ventricle (3v) to target nearby GK-expressing neurons. Four and 6 days after 3v, but not 4v, alloxan injection, alloxan-treated rats ate only 30% and their blood glucose area under the curve was only 28% of saline controls' after systemic 2-deoxy-D-glucose. In addition, their hyperglycemic response to hindbrain glucoprivation induced with 5-thio-glucose was impaired, whereas fasting blood glucose levels and food intake after an overnight fast were elevated. These impaired responses were associated with the destruction of 3v tanycytes, reduced glial fibrillary acidic protein-immunoreactivity surrounding the 3v, neuronal swelling, and decreased arcuate nucleus neuropeptide Y (NPY) mRNA. Nevertheless, hypothalamic GK mRNA was significantly elevated. Two weeks after alloxan injection, 3v tanycyte destruction was reversed along with restoration of feeding and hyperglycemic responses to both systemic and hindbrain glucoprivation. At this time there were significant decreases in GK, NPY, and proopiomelanocortin mRNA. Thus, neural substrates near and around the 3v affected by alloxan may be critically involved in the expression of these glucoprivic responses.