Adrenalectomy improves glycemic responses in congenic obese LA/Ntul//-cp RATS

To determine the effects of adrenalectomy on typical insulin-mediated glycemic responses in male obese rats, groups (n=6 -12 rats/phenotype) of normally reared congenic lean and obese animals were fed a Purina chow diet from 6 to 9 weeks of age, and the Chow diet plus a highly palatable cafeteria diet from 9 to 12 weeks of age. The congenic LA/Ntul//-cp rat strain is noted for its longevity and early expression of the obese trait but remains non-diabetic throughout much if not all of its normal lifespan. Subgroups of obese animals were subjected to bilateral adrenalectomy (ADX) at 6 weeks of age to remove glucocorticoid contributions to glycemic parameters. Measures of weight gain (WG )and of glucose tolerance (OGT) were obtained in the three treatment groups at 6, 9 and 12 weeks of age. WG on ADX-obese rats was similar to that of their lean littermates at 6 and 9 weeks of age on the chow diet but increased to twice that observed in their lean littermates from 9 to 12 weeks of age. OGT responses after 30 to 60 minutes and the area under the OGT curve were impaired but not diabetic in obese animals at all ages compared to lean littermates and returned toward those of normally lean rats after ADX. The Insulin to glucose ratio (I:G) was also consistent with insulin resistance in obese but not in ADX-obese or lean rats at 12 weeks of age. In conclusion, ADX resulted in normalization of OGT and glycemic parameters in the obese phenotype at 9 and 12 weeks of age. These results are consistent with normalization of typical insulin-mediated components of glycemic parameters and glucose uptake in peripheral tissues following adrenalectomy of congenic obese rats. The results further suggest that the counterregulatory effects of insulin and glucocorticoid hormones may be contributory to the impaired glycemic responses in the obese phenotype of the LA/N//-cp (corpulent) rat and are consistent with a receptor-mediated element in the development of insulin resistance and glucose uptake in peripheral tissues commonly associated with the early development of obesity in this strain.

Hepatic LC3 II/I ratio is not modulated in exercised mice

Autophagy plays an essential role in body homeostasis achievement. One of the main proteins involved in this process is the LC3I, which, after lipidation, leads to the formation of LC3II that participates in the formation and maturation of autophagosome. This descriptive study verified the responses of LC3II to LC3I proteins, as well as the time-course of this ratio in mice livers after different types of acute physical exercise protocols. Eight-week-old male C57BL/6 mice were maintained three per cage with controlled temperature (22±2 °C) on a 12:12-h light-dark normal cycle with food (Purina chow) and water ad libitum. Mice were randomly divided into four groups: control (CT, sedentary mice), resistance (RE, submitted to a single bout of resistance exercise), endurance (EE, submitted to a single bout of endurance exercise), and concurrent (CE, submitted to a single bout of endurance combined with resistance exercise). The mice livers were extracted and used for the immunoblotting technique. The hepatic LC3B II/I ratio for the RE and EE groups were not altered during the different time-points. For the CE group, there was a decrease in this ratio 12h after exercise compared to time 0 and 18h. Also, the hepatic LC3B II/I ratios were not different among the acute physical exercise protocols along the time-course. The hepatic LC3B II/I ratio was not influenced by the endurance and resistance protocols but decreased in response to the concurrent protocol at 12h after the stimulus.

MON-692 Effect of High Salt Diet on Kidney Weight in Neonatal Streptozotocin Induced Noninsulin Dependent Diabetic Rats

Diabetic kidney hypertrophy may contribute to the development of diabetic kidney disease. Hyperglycemia is recognized as a cause for the kidney endangerment. Salt may accelerate progression of kidney disease in diabetes. To further study the effect of high salt intake on kidney disease we used neonatal streptozotocin induced Noninsulin Dependent Diabetic (NIDD) rats fed ad libitum with regular Purina chow and 2% salt Purina chow. Rats in 5 groups were sacrificed at 6 weeks. Each group had 5–7 rats of diabetics on 2% salt and on regular chow and controls on 2% salt and on regular chow. Blood glucose in diabetics on salt ranged between 185±19–576±20 and in diabetics on regular chow 184±20–458±78 mg/dl. Controls on 2% salt 105±8.6–133±10.3 and controls on regular chow 110±8.9 - 130±3.11. Kidney weights in diabetics on salt was 1.85±0.09–2.0±0.06 gr, diabetics on regular chow 1.6±0.04 - 1.56±0.06 controls on salt 1.19±0.03–1.32±0.05 and controls on regular chow 1.23±0.03. Blood glucose in diabetics on salt and on regular chow was higher than in controls p˂0.05 but did not differ between the diabetic groups. Kidney weight was increased in both diabetic groups compared with controls p˂0.05 and was increased in diabetics on salt compared with diabetics on regular chow p˂0.05 at all glucose levels. Controls on salt and on regular chow had similar kidney weights. Also kidney weight relative to body weight was higher in diabetics than in controls p˂0.05 and was higher in diabetics on salt compared to diabetics on regular chow p˂0.05, but there was no difference between controls on salt and controls on regular diet. Kidney % of water was similar in all four groups but protein to kidney DNA ratio was higher in the diabetic groups p˂0.05 confirming the kidney hypertrophy. Insulin sensitivity measured in controls was not different between groups when glucose transport, glucose oxidation and lipogenesis were measured in fat cells showing no effect of salt on insulin sensitivity. We suggest that high salt intake is an additional risk factor for increased kidney weight in NIDDM that is additive to that of the prevailing glycemia.

Central CRF inhibits gastric emptying of a nutrient solid meal in rats: the role of CRF2receptors

Corticotropin-releasing factor (CRF)-related peptides exhibit different affinity for the receptor subtypes 1 and 2 cloned in the rat brain. We investigated, in conscious rats, the effects of intracisternal (IC) injection of CRF (rat/human) on the 5-h rate of gastric emptying of a solid nutrient meal (Purina chow and water ad libitum for 3 h) and the CRF receptor subtype involved. CRF, urotensin I (suckerfish), and sauvagine (frog) injected IC inhibited gastric emptying in a dose-dependent manner, with ED50 values of 0.31, 0.13, and 0.08 μg/rat, respectively. Rat CRF-(6—33) (0.1–10 μg ic) had no effect. The nonselective CRF1and CRF2 receptor antagonist, astressin, injected IC completely blocked the inhibitory effect of IC CRF, urotensin I, and sauvagine with antagonist-to-agonist ratios of 3:1, 10:1, and 16:1, respectively. The CRF1-selective receptor antagonist NBI-27914 injected IC at a ratio of 170:1 had no effect. These data show that central CRF and CRF-related peptides are potent inhibitors of gastric emptying of a solid meal with a rank order of potency characteristic of the CRF2receptor subtype affinity (sauvagine > urotensin I > CRF). In addition, the reversal by astressin but not by the CRF1-selective receptor antagonist further supports the view that the CRF2 receptor subtype is primarily involved in central CRF-induced delayed gastric emptying.

Leptin-induced decrease in food intake is not associated with changes in gastric emptying in lean mice

Chronic treatment with leptin regulates body weight and energy balance and reduces food intake in obese and lean mice. In 18- to 20-h fasted lean mice (C57BL/6, +/+), we examined the acute effect of a single intraperitoneal injection of recombinant mouse leptin (0.12 mg/kg) on food intake and gastric emptying. Leptin reduced food intake, with a peak inhibition at the 5th h postinjection (69 +/- 12%/h), although there was no change in food consumption at the 1st h. Leptin did not alter the 4-h rate of gastric emptying of a solid nutrient meal (free access to Purina chow for either 1-, 2-, or 4-h period). In normal Sprague-Dawley rats fasted for 18-20 h, a single intraperitoneal injection of recombinant mouse leptin (0.2 or 1.2 mg/kg) did not modify the 7-h cumulative or hourly food intake. These results show that a single intraperitoneal injection of recombinant mouse leptin reduces food intake within 5 h while not influencing gastric emptying of ingested food in lean mice. Sprague-Dawley rats are unresponsive to the food intake-reducing effect of a single intraperitoneal injection of mouse leptin at a dose 10-fold higher than that shown to be effective in mice within the first 4-7 h postinjection.

Female sex steroid induced gallbladder epithelium changes and gallstone deposits in female hamsters: TEM and SEM aspects

Approximately 1 million people in the United States alone develop gallstones each year. The incidence is higher in women than in men and the ratio being 4 ≥ 1. A correlation has also been suggested between oral contraceptives and cholelithiasis. In addition, postmenopausal or cancer estrogen therapy has been reported to be a factor responsible for gallstone formation. Female sex hormone receptors have been detected not only in the gallbladder musculature, but also in its epithelium. As a follow up to experiments effectuated in the male and the ovariectomized Syrian hamster, this report shows that, a combination of a low cholesterol diet with female sex steroid treatment contributes to the formation of gallstone-like deposits, while modifying the surface epithelium morphology. Syrian hamsters (F1B strain, BioBreeders, Watertown MA) were housed under 12h light: 12 h dark cycle, at 20 °C, fed Purina chow and water ad libitum. Several duration/treatment groups were studied, but this report will focus on data obtained with the group injected weekly with estradiol valerate (E weekly, s.c. 8-10 μg/100 g.b.w., in corn oil) and with i.m. medroxyprogesterone acetate (DepoProvera Upjohn Co., Kalamazoo, MI; 8-10 mg/100 g.b.w.) for a 3-month period. Other parameters (blood and bile) were also studied but not reported here.

Hypocholesterolaemic effect of β β'-methyl-substituted hexadecanedioic acid (MEDICA 16) in the male hamster

Treatment of cholesterol-fed male hamsters kept on a diet of purina chow with beta beta'-methyl-substituted hexadecanedioic acid (MEDICA 16) resulted in a progressive hypocholesterolaemic effect, amounting to a 50% decrease in the cholesterol content of all plasma lipoproteins. The decrease in plasma cholesterol could be accounted for by activation of plasma-cholesterol efflux through the liver into the bile mediated by MEDICA 16-induced (a) increase of the number of liver LDL receptors, (b) activation of liver neutral cholesteryl ester hydrolase with a concomitant inhibition of liver acyl-CoA cholesterol acyltransferase, resulting in shifting of the liver cholesteryl ester/free-cholesterol cycle in the direction of free cholesterol, and (c) activation of cholesterol efflux from the liver into the bile. The increase in bile cholesterol output was accompanied by an increase in bile phospholipids but not in bile acids. In contrast with rats, MEDICA 16-treatment of male hamsters did not result in a hypotriacylglycerolaemic effect, inhibition of lipogenesis, nor in a substantial decrease in plasma apolipoprotein C-III content.

Damage To Endothelial Cells In The Ear Artery Of Rabbits On An Atherogenic Diet

Male New Zealand rabbits were fed a diet containing 2% cholesterol, 6% peanut oil and 92% Purina Chow for periods between 6 and 9 weeks. Examination of the inner surface of the central ear artery by scanning electron microscopy (after perfusion in situ with Tyrode’s solution followed by 1% glutaraldehyde) revealed damage to the endothelium which appeared to be considerably worse at 9 weeks than at 6 weeks. At six weeks the damage included irregularly shaped cells, some breaks at intercellular junctions and occasional holes in the cells. At 9 weeks more severe damage was seen. This included many misshapen cells, cells with holes, and many cells lifting off from the vessel wall and beginning to expose sub-endothelial tissue. In 3 rabbits (respectively on the diet for 6,7 or 9 weeks) arrays of dark “spots” were seen in many cells. Such “spots” were never seen in endothelial cells of normal rabbits. After 1 ml of 0.83 mM sodium arachidonate (AA), instead of Tyrode’s solution, had been perfused through the arteries, further damage was seen. This damage included the lifting off of many cells and formation of many holes. Effluent from the arteries perfused with AA contained 6-keto-PGF1α and TxB2 (measured by specific radioimmunoassays) in amounts similar to those produced by arteries of rabbits fed a normal diet. These metabolites were not detected in effluents of arteries perfused with Tyrode’s solution.This report shows that an atherogenic diet may cause early morphological changes in a peripheral artery of the rabbit and suggests that widespread damage to arterial endothelium may result from atherogenic diets. Apparently, this damage does not impair the ability of the vessel wall to convert AA into prostacyclin. The rabbit ear artery system appears to be a simpler way to study the early changes in arterial endothelium during experimental atherosclerosis than studies on the aorta.

Effect of diet and drugs on the qualitative and quantitative distribution of cytochromes P-450 in rat liver

Male Sprague–Dawley rats were fed either Purina chow or a nutritionally adequate liquid control diet containing either 4 or 38% of the total caloric intake as fat. The hepatic cytochromes P-450 were induced in these animals either by the administration of phenobarbital, β-naphthoflavone, or isocaloric replacement of the carbohydrate of the liquid diets by ethanol at a level of 36% of total calories for 4 or 6 weeks. Three distinct groups of cytochromes P-450 could be efficiently separated by ion-exchange chromatography of microsomal preparations from these rats. The concentration of each group of cytochromes P-450 was markedly affected by variations in lipid and carbohydrate content of the diet as well as by administration of drugs.

Enhanced in vitro hepatic glucuronidation of thyroxine in rats following cutaneous application or ingestion of polychlorinated biphenyls

In rats four daily skin applications of a 30% solution of a polychlorinated biphenyl (PCB) mixture in mineral oil or of a microscope immersion oil, containing 34% PCB, led to increases in liver weight, protein concentration of the 10 000 × g supernatant fluid of liver homogenates and the in vitro glucuronidation of thyroxine (T4) by the supernatant fluid, whether related to liver weight or to protein concentration in the reaction mixture. Similar effects occurred after feeding 250 ppm (mg/kg) of PCB in either Purina chow or a low-iodine diet for 11 days. It is concluded that increased hepatic T4 glucuronidation contributes to the enhanced biliary excretion of T4 previously observed in PCB-treated rats.