Kaempferol protects against streptozotocin-induced diabetic cardiomyopathy in rats by a hypoglycemic effect and upregulating SIRT1.

This study investigated if kaempferol could attenuate the oxidative, inflammatory, and fibrotic damage of the left ventricles (LVs) in streptozotocin (STZ)-diabetic rats by modulating silent mating type information regulation 2 homolog 1 (SIRT1) signaling. Adult male rats were divided into 5 groups (n = 12/each) as control, control + kaempferol, STZ-induced diabetes mellitus (STZ-DM), STZ-DM + kaempferol, and STZ-DM + kaempferol + EX-527, a sirtuin 1 (SIRT1) inhibitor. Administration of kaempferol to diabetic rats significantly preserved the systolic and diastolic functions of the LVs that was associated with a significant reduction in ventricular collagen deposition, infiltration of inflammatory cells, and protein expression of Bcl2-associated X protein (Bax), cleaved caspase-3, and cytochrome-C. In both the control and diabetic rats, kaempferol attenuated the loss in body weights, reduced fasting glucose levels, and increased fasting insulin levels and HOMA-ß. Besides, kaempferol lowered the levels of reactive oxygen species (ROS), malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6), downregulated the transforming growth factor-ß1 (TGF-ß1) and reduced the nuclear levels of NF-κB p65. In concomitant, kaempferol increased the LV levels of manganese superoxide dismutase (MnSOD) and glutathione (GSH) and stimulated the total protein levels of Bcl2, the nuclear activity of SIRT1, and nuclear levels of nuclear factor erythroid 2-related factor 2 (Nrf2). These events were associated with increased deacetylase activity and total levels of SIRT1 and a parallel decrease in the acetylation of Nrf2, NF-κB, smad2, and FOXO1. In conclusion: kaempferol attenuate diabetic cardiomyopathy in STZ-treated rats through its hypoglycaemic and insulin-releasing effects, as well as a cardiac independent mechanism that involves activation of SIRT1.

Hepatoprotective and Antioxidant Activity of Dunaliella salina in Paracetamol-induced Acute Toxicity in Rats.

Paracetamol has a reasonable safety profile when taken in therapeutic doses. However, it could induce hepatotoxicity and even more severe fatal acute hepatic damage when taken in an overdose. The green alga, Dunaliella salina was investigated for hepatoprotective and antioxidant activity against paracetamol-induced liver damage in rats. Male albino Wistar rats overdosed with paracetamol showed liver damage and oxidative stress as indicated by significantly (P<0.05) increased serum levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total and direct bilirubin, malondialdehyde, cholesterol and nitric oxide. At the same time, there were decreased activities of serum superoxide dismutase and total antioxidant capacity compared with the control group. Treatment with D. salina methanol extract at doses of 500 and 1000 mg/kg body weight or silymarin could significantly (P<0.05) decrease the liver damage marker enzymes, total and direct bilirubin, malondialdehyde, cholesterol and nitric oxide levels and increase the activities of superoxide dismutase and total antioxidant capacity in serum when compared with paracetamol intoxicated group. Liver histopathology also showed that D. salina reduced the centrilobular necrosis, congestion and inflammatory cell infiltration evoked by paracetamol overdose. These results suggest that D. salina exhibits a potent hepatoprotective effect on paracetamol-induced liver damage in rats, which may be due to both the increase of antioxidant enzymes activity and inhibition of lipid peroxidation.

Metabotropic glutamate receptor subtype-1 is essential for in vivo growth of melanoma.

Ectopic expression of metabotropic glutamate receptor subtype 1 (mGluR1) in mouse melanocytes induces melanoma formation. Although requirement of mGluR1 for development of melanoma in the initial stage has been demonstrated, its role in melanoma growth in vivo remains unclear. In this study, we developed novel transgenic mice that conditionally express mGluR1 in melanocytes, using a tetracycline regulatory system. Pigmented lesions on the ears and tails of the transgenic mice began to appear 29 weeks after activation of the mGluR1 transgene, and the transgenic mice produced melanomas at a frequency of 100% 52 weeks after transgene activation. Subsequent inactivation of the mGluR1 transgene in melanoma-bearing mice inhibited melanoma growth with reduction of immunoreactivity to phosphorylated ERK1/2, whereas mice with persistent expression of mGluR1 developed larger melanoma burdens. mGluR1 expression is thus required not only for melanoma development but also for melanoma growth in vivo. These findings suggest that growth of melanoma can be inhibited in vivo by eliminating only one of the multiple genetic anomalies involved in tumorigenesis.

The influence of sex, age, synthetic oestrogens, progestogens and oral contraceptives on the excretion of urinary tryptophan metabolites.

PIP: The excretion of urinary tryptophan metabolites was studied in normal and postmenopausal women and in women taking norethindrone and ethinyl estradiol, singly and in combination. The results showed that the altered tryptophan metabolism found in the preovulatory phase of the cycle and in postmenopausal women was the result of an interaction between Vitamin-B6 and endogenous sex hormones. During the preovulatory phase, endogenous estradiol disrupted the normal activity of the Vitamin-B6-dependent quinolinic acid decarboxylase, which resulted in the accumulation of bladder carcinogens in urine. During the postovulatory phase, endogenous progesterone and the production of metabolites antagonized this effect. Administration of naturally occurring progesterone and of ethinyl estradiol, alone and in combination with norethindrone, was able to counter the interaction between Vitamin-B6 and endogenous estradiol. It is suggested that the cyclic excretion pattern of endogenous bladder carcinogens in young, nonpregnant women may contribute, in part, to the low incidence of bladder cancer in women.^ieng

Studies with tryptophan metabolites in vitro. Kynurenine metabolism in kidneys of mice infested with Schistosoma mansoni.

The conversion in vitro of kynurenine into kynurenic acid and anthranilic acid in both normal kidneys and those obtained from mice infested with Schistosoma mansoni was investigated. Normal mouse kidneys seem to possess an excess of functional pyridoxal phosphate over those obtained from infested mice. Kynureninase and kynurenine transaminase in the latter kidneys are more easily inhibited by deoxypyridoxal phosphate and tartar emetic, indicating low stores of active pyridoxal phosphate. The possible implication of these findings in relation to the role of the kidneys in producing abnormal patterns of tryptophan metabolism and possibly contributing to the production of bladder tumours in bilharzial patients is discussed.

Studies with tryptophan metabolites in vitro. Kynurenine metabolism in liver homogenates of normal and Schistosoma mansoni-infested mice.

The conversion of kynurenine into kynurenic acid and anthranilic acid in both normal and Schistosoma mansoni-infested mouse liver was investigated. It was found that in the S. mansoni-infested mouse liver there is probably a deficiency of pyridoxal phosphate that resulted in an inhibition of kynurenine transaminase and a low production of kynurenic acid. Deoxypyridoxine and its phosphorylated derivative inhibited kynurenine transaminase in the normal liver in a pattern qualitatively similar to that observed with infested liver. The lowered concentration of pyridoxal phosphate in the infested liver is discussed in view of the possibility of two combined mechanisms: (a) an antimetabolite being secreted by the infesting worms or present in its eggs that partially inhibited the phosphorylation of pyridoxal, and (b) concentration of pyridoxal phosphate by the worms, resulting in a lowered concentration of the cofactor in the host tissue.