Studies of liver lipids in normal, alloxan-diabetic and pregnancy-toxaemic sheep

N-acetyl-β-d-glucosaminidase activity assay for monitoring insulin-dependent diabetes using Ag-porous Si SERS platform

Determination of urinary or serum N-acetyl-β-d-glucosaminidase (NAG) activity as a tissue damage indicator is widely used in diagnosis of various pathologies, including diabetic nephropathy. Early and rapid biomarker detection is an important element of medical diagnosis, facilitating prompt therapeutic decisions and prognosis evaluation. Herein, we present a modified sensing approach for a rapid and reliable NAG activity determination in complex media using surface-enhanced Raman spectroscopy (SERS). Porous silicon (PSi) Fabry-Pérot interferometers were redesigned as sensitive SERS platforms utilizing the vast inherent surface area for silver (Ag) nanoparticles embedment. Interaction of the porous nanostructures with specific NAG-enzymatic products produces an indicative spectral fingerprint proportional in magnitude to its concentration. The sensitivity of Ag-PSi SERS substrates was evaluated in complex matrices presenting sufficient limits of detection compared with other advanced assays and techniques (0.07, 0.47 and 0.50 mU mL^-1 for urine, milk and plasma, respectively). The augmented optical performance revealed recovery values of 96-109%, indicating successful and selective NAG recognition in biological fluids. Finally, the potential applicability of the suggested prototype for real-life scenarios was evaluated in vivo, in a model of insulin-dependent diabetes induced in sheep. Overall, the robust data confirm the application of SERS analysis for early diagnosis of pathology and for evaluation of clinical responses to pharmacological treatments.

Improved Folch Method for Liver-Fat Quantification

Fatty liver represents a significant metabolic pathology of excess intrahepatic fat in domestic animals and humans. Quantification of hepatic-fat content is therefore essential for diagnosis and investigation of liver and metabolic disease. However, the reproducibility of hepatic steatosis analysis is often low due to subjective and technical factors. We hypothesized that improvement in tissue-lipids extraction efficiency would contribute to the accuracy and precision of liver-fat determination. To test it, we investigated the effect of standardized tissue sonication on liver-fat quantification by the Folch method in sheep. Liver samples from grownup lambs of lean (n = 16) and fatty (n = 15) livers, and from pregnant ewes (n = 6) who died from pregnancy toxemia (PT), were used for hepatic-fat content determination with or without tissue sonication. In the grown lambs, an average hepatic-fat content of 6.6% was determined in sonicated compared to 5.1% in non-sonicated specimens (P = 0.0002). Similarly, in ewes with PT, an average of 12.5% was determined with sonication compared to 10.8% without it (P = 0.0006), and the reproducibility was higher with sonication (CV of 3.1 vs. 6.1%, respectively). Thus, tissue sonication improved the efficiency of liver-lipids extraction and was significant to the accuracy and precision of hepatic-fat determination. Enzymatic quantification of triglycerides was moderately correlated with the results obtained gravimetrically (r = 0.632, P < 0.005). The reported data provide reliable reference values for pregnancy toxemic sheep. The significant improvement in liver-fat quantification observed with the reported revised protocol is likely applicable to most mammals and humans.

Arachidonic acid and lipoxin A4 attenuate alloxan-induced cytotoxicity to RIN5F cells in vitro and type 1 diabetes mellitus in vivo

OBJECTIVE

We studied whether polyunsaturated fatty acids (PUFAs) can protect rat insulinoma (RIN5F) cells against alloxan-induced apoptosis in vitro and type 1 diabetes mellitus (type 1 DM) in vivo and if so, mechanism of this beneficial action.

MATERIAL AND METHODS

In vitro study was conducted using RIN5F cells while in vivo study was performed in Wistar rats. The effect of PUFAs, cyclo-oxygenase and lipoxygenase inhibitors, various eicosanoids and PUFAs metabolites: lipoxin A4 (LXA4), resolvin D2 and protectin against alloxan-induced cytotoxicity to RIN5F cells and type 1 DM was studied. Expression of PDX1, P65 NF-kB and IKB in RIN5F cells and Nrf2, GLUT2, COX2, iNOS protein levels in the pancreatic tissue and plasma glucose, insulin and tumor necrosis factor-α and antioxidants, lipid peroxides and nitric oxide were measured.

RESULTS

Of all, arachidonic acid (AA) was found to be the most effective against alloxan-induced cytotoxicity to RIN5F cells and preventing type 1 DM. Both cyclo-oxygenase and lipoxygenase inhibitors did not block the beneficial actions of AA in vitro and in vivo. Alloxan inhibited LXA4 production by RIN5F cells and in alloxan-induced type 1 DM Wistar rats. AA-treatment restored LXA4 levels to normal both in vitro and in vivo. LXA4 protected RIN5F cells against alloxan-induced cytotoxicity and prevented type 1 DM and restored expression of Nrf2, Glut2, COX2, and iNOS genes and abnormal antioxidants to near normal.

DISCUSSION

AA seems to bring about its beneficial actions against alloxan-induced cytotoxicity and type 1 DM by enhancing the production of LXA4. © 2016 BioFactors, 43(2):251-271, 2017.

Hepatic Lipidosis and other Test Findings in Two Captive Adult Porcupines (Erethizon Dorsatum) Dying from a “Sudden Death Syndrome”

Routine postmortem examination and histologic evaluation of tissue sections demonstrated hepatic lipidosis (HL) in 2 adult captive porcupines with a history of sudden death. The male porcupine had a markedly enlarged pale liver that microscopically showed large unilocular vacuoles within hepatocellular cytoplasm. The periparturient female had similar but less marked hepatic lesions and an incidental pulmonary mycosis. These findings suggest HL as an important differential of spontaneous death in captive porcupines. It is hypothesized that in addition to the widely documented causes, HL in captive porcupines may be specifically associated with nutritional imbalances caused by the feeding of unsuitable commercial diets. The possible association of the condition with dietary and other factors in captive porcupines needs to be thoroughly investigated.

Spontaneous pregnancy toxaemia (ketosis) in sheep and the role of insulin

214 ewes suffering from pregnancy toxaemia (ketosis) were examined. Clinical signs during onset and course of disease and laboratory findings were compared between animals that survived and those which died. In the latter the onset of ketosis was earlier in pregnancy (day 143 +/- 7 vs. day 146 +/- 8) and duration of the disease was shorter (10 +/- 13 vs. 14 +/- 9 days). The animals that died showed more severe clinical signs and higher values of 3-hydroxy-butyrate (4.3 +/- 3.6 vs. 3.5 +/- 2.6 mmol/l) and cortisol (72 +/- 98 vs. 52 +/- 80 mmol/l) as well as lower values of insulin (37 + 12 vs. 3.5 + 2.6 mmol/l) and potassium (4.1 + 1.0 vs. 4.4 + 1.0 mmol/1) at onset of the disease than those which survived (all of differences with P < 0.05). Glucose levels did not differ between groups. Treated animals with glucose plus fructose infusions (n = 56) or with oral application of glucose precursors plus electrolytes (n = 126) had survival rates of 53.6% and 62.7%, respectively. Oral treatment with glucose precursors plus electrolytes and an additional subcutaneous insulin treatment (n = 15) led to an enhanced survival rate of 86.7% (P < 0.05). Low insulin levels in ketotic pregnant sheep and the therapeutic effect of insulin treatment support the hypothesis that insulin plays a causative role in the pathogenesis of ovine ketosis.

Effects of estradiol-17 beta on the net hepatic extraction of triglyceride in vivo in fed and fasted sheep

The effects of estrogen and fasting on hepatic metabolism were studied by an arteriovenous difference technique in six multicatheterized ewes. In each experiment samples were collected during fed and 3- and 5-day fasted states before, and 10 to 17 days after the animals had been implanted with 550 mg of estradiol-17 beta. The implants elevated plasma estradiol five- to seven-fold. Plasma concentrations of insulin and triglyceride (TG) were increased (P less than 0.01) by 131% and 62% respectively by estradiol in fed sheep. Concurrent circulating concentrations of glucose, glycerol, free fatty acids, and beta-hydroxybutyrate were unaffected. During fasting estradiol elevated circulating concentrations of beta-hydroxybutyrate slightly, while levels of other metabolites and insulin were not different from fasted controls. In fed animals estradiol had no effect on the net hepatic uptake (NHU) of TG or glycerol but during fasting estradiol reduced the NHU of TG and glycerol by 47% and 31% (P less than 0.01) respectively. In addition, estradiol reduced the net hepatic production of beta-hydroxybutyrate in fed, but not in fasted animals. Net hepatic exchanges of glucose, or FFA were not affected by estradiol in either the fed or fasted state. Fasting increased the NHU of TG (P less than 0.05) and glycerol (P less than 0.01). The results of this study suggest that estradiol, at physiological concentrations, has lipotropic and anti-ketogenic effects on the ruminant liver. However, the anti-ketogenic effect is not apparent in fasted animals. Secondly, it appears that the hepatic lipidosis which often occurs in ruminants during negative energy balance is due largely to an increase in the NHU of circulating TG.

Fatty acid metabolism of the perfused caudate lobe from livers of fed and fasted non-pregnant and fasted late pregnant ewes

1. Fatty acid metabolism has been compared in perfused liver lobes from fed and fasted non-pregnant sheep and fasted pregnant sheep to provide further information on the control of ketogenesis in this species. 2. Ketogenesis from exogenous palmitate was greatest in lobes from fasted pregnant sheep and least in lobes from fed non-pregnant sheep, whereas rates of ketogenesis from exogenous octanoate (0.4 mM) were similar in lobes from sheep in all three states. 3. High rates of ketogenesis from endogenous fatty acids occurred in perfused lobes from fasted pregnant sheep, apparently owing to enhanced lipolysis. 4. Activities of glycerol-3-phosphate acyltransferase, carnitine palmitoyl transferase (CPT) and other enzymes involved in ketone production did not change with physiological state; sheep differ markedly from rats in this respect. 5. The results suggest that the primary point of control of ketogenesis within the liver of sheep is at the level of CPT; the lack of change in maximum CPT activity suggests that control by modulators of this enzyme activity is even more important in sheep than in rats.

Plasma triacylglycerol secretion in sheep. Paradoxical effects of fasting and alloxan diabetes

Plasma triacylglycerol and phospholipid concentrations were increased in fasting and diabetic sheep compared with fed animals. Secretion was measured in these animals using Triton WR1339 to block lipoprotein lipase. Triacylglycerol secretion was lowest in fed animals and, unlike non-ruminant species, increased by fasting and diabetes. These changes were in proportion to plasma free fatty acid concentration. However, no effect of Triton was found on plasma phospholipids under any of the conditions studied. It is suggested that the low rate of triacylglycerol secretion in normal animals is due to the limiting membrane found in the liver sinusoid of the sheep and that the greater rate in fasting and diabetes reflects the increased mass of intrahepatic triacylglycerol.