Repurposing Pitavastatin and L-Glutamine: Replenishing β-Cells in Hyperlipidemic Type 2 Diabetes Mouse Model

Type 2 diabetes (T2D) is associated with obesity and declining β-cells. L-glutamine has been implicated in the amelioration of T2D by virtue of its incretin secretagogue property while, there are mixed reports on pitavastatin’s adiponectin potentiating ability. We aimed to investigate the effect of pitavastatin (P), L-glutamine (LG), and combination (P + LG) on glycemic control and β-cell regeneration in a high-fat diet (HFD) + streptozotocin (STZ)-induced T2D mouse model. C57BL6/J mice treated with HFD + STZ were divided into four groups: diabetes control (HFD + STZ), P, LG, and P + LG, while the control group (NCD) was fed with the normal-chow diet. Significant amelioration was observed in the combination therapy as compared to monotherapies in respect of (i) insulin resistance, glucose intolerance, lipid profile, adiponectin levels, and mitochondrial complexes I, II, and III activities, (ii) reduced phosphoenolpyruvate carboxykinase, glucose 6-phophatase, glycogen phosphorylase, and GLUT2 transcript levels with increased glycogen content in the liver, (iii) restoration of insulin receptor 1β, pAkt/Akt, and AdipoR1 protein levels in skeletal muscle, and (iv) significant increase in islet number due to β-cell regeneration and reduced β-cell death. L-glutamine and pitavastatin in combination can ameliorate T2D by inducing β-cell regeneration and regulating glucose homeostasis.

Calorie restriction potentiates the therapeutic potential of GABA in managing type 2 diabetes in a mouse model

Dysfunctional adipocytes/β-cells advance type 2 diabetes (T2D). Calorie restriction (CR) improves insulin sensitivity and fasting blood glucose (FBG) levels, while γ-aminobutyric acid (GABA) exerts regenerative effects. The impact of therapies was assessed by a high-fat diet (HFD) + streptozotocin (STZ) induced T2D mouse model. The mice were fed a CR diet (30% reduction of HFD) and treated with GABA (2.5 mg/kg i.p) for 5 weeks. Standard protocols were used to assess metabolic parameters. The mRNA expression was monitored by SYBR Green-qPCR in the targeted tissues. Oxygen consumption rate in the mitochondrial complexes was evaluated by oxytherm clark-type oxygen electrode. Pancreatic β-cell regeneration and apoptosis were analysed by immunohistochemistry. CR + GABA combination therapy showed improved metabolic parameters compared to the monotherapies. We have observed improved transcript levels of G6Pase, PEPCK, Glycogen Phosphorylase, GLUT2 and GCK in liver; ACC and ATGL in adipose tissue. Also increased SIRT-1, PGC-1α and TFAM expression; up-regulated mitochondrial complexes I-III activities were observed. We have seen increased BrdU/Insulin and PDX1/Ngn3/Insulin co-positive cells in CR + GABA treated group with a reduction in apoptotic marker (TUNEL/Insulin co-positive cells). Our results indicate that CR in combination with GABA ameliorates T2D in HFD + STZ treated mice by GABA induced β-cell regeneration, and CR mediated insulin sensitivity.

Diabetes mellitus and melatonin: Where are we?

Diabetes mellitus (DM) and diabetes-related complications are amongst the leading causes of mortality worldwide. The international diabetes federation (IDF) has estimated 592 million people to suffer from DM by 2035. Hence, finding a novel biomolecule that can effectively aid diabetes management is vital, as other existing drugs have numerous side effects. Melatonin, a pineal hormone having antioxidative and anti-inflammatory properties, has been implicated in circadian dysrhythmia-linked DM. Reduced levels of melatonin and a functional link between melatonin and insulin are implicated in the pathogenesis of type 2 diabetes (T2D) Additionally, genomic studies revealed that rare variants in melatonin receptor 1b (MTNR1B) are also associated with impaired glucose tolerance and increased risk of T2D. Moreover, exogenous melatonin treatment in cell lines, rodent models, and diabetic patients has shown a potent effect in alleviating diabetes and other related complications. This highlights the role of melatonin in glucose homeostasis. However, there are also contradictory reports on the effects of melatonin supplementation. Thus, it is essential to explore if melatonin can be taken from bench to bedside for diabetes management. This review summarizes the therapeutic potential of melatonin in various diabetic models and whether it can be considered a safe drug for managing diabetic complications and diabetic manifestations like oxidative stress, inflammation, ER stress, mitochondrial dysfunction, metabolic dysregulation, etc.

Endocrine Disruptors-'Food' for Thought

Green vegetables, fruits, cereals, and pulses are all rich sources of antioxidants. Retinoic acid, ascorbate, proanthocyanidins, tannins, saponins, melatonin, curcumin, allicin, and alpha-lipoic acid stand documented in plants as bioactive compounds. The international dietary committee advocates a specific quantum of these natural antioxidants through diet. Interestingly, environmental pollution has indeed affected most of these farm products. The use of chemical fertilizers, pesticides and heavy metals in soil has a cumulative effect on human health. Enough evidence is available for the presence of phytoestrogen, xenoestrogen, and a host of other endocrine disruptors in the food. These plant-based nutrients can mimic or enhance the natural hormone's health effects. While endocrine disruptors are found in many everyday products, this review aims to address endocrine disruptors from food in the Asian subcontinent. 'Food for thought' justifies the paradigm shift towards good endocrine health by swaying away from the conventional daily dietary recommendations.

β-cell replenishment: Possible curative approaches for diabetes mellitus

AIMS

Diabetes mellitus (DM) is a disorder of heterogeneous etiology marked by persistent hyperglycemia. Exogenous insulin is the only treatment for type 1 diabetes (T1D). Islet transplantation is a potential long cure for T1D but is disapproved due to the possibility of immune rejection in the later stage. The approaches used for treating type 2 diabetes (T2D) include diet restrictions, weight management and pharmacological interventions. These procedures have not been able to boost the quality of life for diabetic patients owing to the complexity of the disorder.

DATA SYNTHESIS

Hence, research has embarked on permanent ways of managing, or even curing the disease. One of the possible approaches to restore the pancreas with new glucose-responsive β-cells is by their regeneration. Regeneration of β-cells include islet neogenesis, dedifferentiation, and trans-differentiation of the already differentiated cells.

CONCLUSIONS

This review briefly describes the islet development, functions of β-cells, mechanism and factors involved in β-cell death. It further elaborates on the potential of the existing and possible therapeutic modalities involved in the in-vivo replenishment of β-cells with a focus on exercise, diet, hormones, small molecules, and phytochemicals.

Intron specific polymorphic site of vaspin gene along with vaspin circulatory levels can influence pathophysiology of type 2 diabetes

Vaspin, an insulin-sensitizing adipokine, has been associated with type 2 diabetes (T2D). The present study aimed to investigate the distribution of genotypes and high-risk alleles of vaspin genetic variants (rs77060950 G/T and rs2236242 A/T), in Gujarat subpopulation (India). Genomic DNA isolated from PBMCs was used to genotype vaspin polymorphisms by PCR-RFLP and ARMS-PCR from 502 controls and 478 patients. RNA isolated from visceral adipose tissue (VAT) of 22 controls and 20 patients was used to assess vaspin transcript levels by qPCR while the vaspin titre of the subjects was assayed using ELISA. Phenotypic characteristics of Fasting Blood Glucose (FBG), BMI and plasma lipid profile were estimated and analyzed for the genotype-phenotype correlation. We identified a significant association of rs2236242 A/T with T2D as the TT genotype conferred a 3.087-fold increased risk. The TT genotype showed association with increased FBG, BMI and Triglycerides levels. Increased GA, GT and TA haplotype frequencies, decreased VAT transcript and vaspin protein levels in T2D patients was observed, which were further negatively correlated with FBG and BMI. In conclusion, rs2274907 A/T polymorphism is strongly associated with reduced vaspin transcript and protein levels, and related metabolic alterations that may play a role in the advancement of T2D.

Treatment Avenues for Type 2 Diabetes and Current Perspectives on Adipokines

BACKGROUND

Diabetes has turned into a pandemic disorder that is affecting millions of people worldwide. Industries are aggressively racing and pursuing research towards the discovery of antidiabetic drug and the current global sale of such drugs are ever on the increase. However, in spite of such massive level of expenditure thereof, WHO projects that by 2030, diabetes will rank as the 7th leading cause of mortality.

OBJECTIVE

It is in this context that we have reviewed here the various approaches available and possible towards diabetes management. This review also includes the WHO guidelines for controlling the glycemic levels, which must be known and followed by clinicians for a better diabetes management.

CONCLUSION

Despite having a wealth of FDA-approved therapeutic options for type 2 diabetes majorities of the patients are not able to achieve the appropriate glycemic control due to various factors. The development of new options with actions at multiple foci of diabetic manifestation and better efficacy may potentially help in improving the current scenario of T2D management.

Melatonin protects against chromium (VI) induced hepatic oxidative stress and toxicity: Duration dependent study with realistic dosage

The present study was undertaken to assess the degree of oxidative stress and toxic effects induced by chromium on hepatic tissue in male Wistar rats exposed to a realistic dosage of Cr(VI) (20 mg/kg/b.w./day) through drinking water, based on the levels of these metals found in the environment, for a duration of 15, 30 and 60 days. The protective effect of melatonin (10 mg/kg) was also studied by simultaneous administration with the metal. Levels of enzymatic and non-enzymatic antioxidants as well as lipid peroxidation were assessed. There was a significant decrease in enzymatic as well as non-enzymatic antioxidants and an increase in the lipid peroxidation level, which were prevented and maintained at near-normal levels by the administration of melatonin in all treatment periods. Metal accumulation was maximal at 15 days, with gradual decreases till 60 days. Histopathological observations also demonstrated the fact that Cr (VI) exposure leads to cytological lesions in the hepatic tissue promoting cellular necrotic/apoptotic changes, while melatonin was able to counteract insults induced by Cr (VI) at all treatment periods. It also prevented alterations in insulin and glucose levels. Overall, the present study suggests a duration-dependent effect of Cr on hepatic oxidative stress and cytotoxicity and shows the potent activity of melatonin in preventing the negative effects of Cr (VI).

Association of Neuropeptide-Y (NPY) and Interleukin-1beta (IL1B), Genotype-Phenotype Correlation and Plasma Lipids with Type-II Diabetes

BACKGROUND

Neuropeptide Y (NPY) is known to play a role in the regulation of satiety, energy balance, body weight, and insulin release. Interleukin-1beta (IL1B) has been associated with loss of beta-cell mass in type-II diabetes (TIID).

OBJECTIVES

The present study attempts to investigate the association of NPY exon2 +1128 T/C (Leu7Pro; rs16139), NPY promoter -399 T/C (rs16147) and IL1B -511 C/T (rs16944) polymorphisms with TIID and their correlation with plasma lipid levels, BMI, and IL1B transcript levels.

METHODS

PCR-RFLP was used for genotyping these polymorphisms in a case-control study involving 558 TIID patients and 1085 healthy age-matched controls from Gujarat. Linkage disequilibrium and haplotype analysis of the NPY polymorphic sites were performed to assess their association with TIID. IL1B transcript levels in PBMCs were also assessed in 108 controls and 101 patients using real-time PCR.

RESULTS

Our results show significant association of both structural and promoter polymorphisms of NPY (p<0.0001 and p<0.0001 respectively) in patients with TIID. However, the IL1B C/T polymorphism did not show any association (p = 0.3797) with TIID patients. Haplotype analysis revealed more frequent association of CC and CT haplotypes (p = 3.34 x 10-5, p = 6.04 x 10-9) in diabetics compared to controls and increased the risk of diabetes by 3.02 and 2.088 respectively. Transcript levels of IL1B were significantly higher (p<0.0001) in patients as compared to controls. Genotype-phenotype correlation of IL1B polymorphism did not show any association with its higher transcript levels. In addition, NPY +1128 T/C polymorphism was found to be associated with increased plasma LDL levels (p = 0.01).

CONCLUSION

The present study provides an evidence for a strong correlation between structural and promoter polymorphisms of NPY gene and upregulation of IL1B transcript levels with susceptibility to TIID and altering the lipid metabolism in Gujarat population.

Vitiligo: interplay between oxidative stress and immune system

Vitiligo is a multifactorial polygenic disorder with a complex pathogenesis, linked with both genetic and non-genetic factors. The precise modus operandi for vitiligo pathogenesis has remained elusive. Theories regarding loss of melanocytes are based on autoimmune, cytotoxic, oxidant-antioxidant and neural mechanisms. Reactive oxygen species (ROS) in excess have been documented in active vitiligo skin. Numerous proteins in addition to tyrosinase are affected. It is possible that oxidative stress is one among the main principal causes of vitiligo. However, there also exists ample evidence for altered immunological processes in vitiligo, particularly in chronic and progressive conditions. Both innate and adaptive arms of the immune system appear to be involved as a primary event or as a secondary promotive consequence. There is speculation on the interplay, if any, between ROS and the immune system in the pathogenesis of vitiligo. The article focuses on the scientific evidences linking oxidative stress and immune system to vitiligo pathogenesis giving credence to a convergent terminal pathway of oxidative stress-autoimmunity-mediated melanocyte loss.

Anthocyanin-rich red cabbage (Brassica oleracea L.) extract attenuates cardiac and hepatic oxidative stress in rats fed an atherogenic diet

BACKGROUND

Oxidative stress induced by reactive oxygen species plays an important role in the aetiology of several diseases including atherosclerosis and coronary heart disease. Anthocyanin-rich extracts have been shown to possess a variety of therapeutic roles, including antioxidant, cardioprotective and hepatoprotective properties. The present inventory was undertaken to evaluate the protective role of anthocyanin-rich red cabbage extract (ARCE) on an atherogenic (ATH) diet-induced hypercholesterolaemia and related cardiac and, hepatic oxidative stress in rats.

RESULTS

ARCE (100 mg kg(-1) body weight) treatment of rats fed the ATH diet significantly prevented elevation in serum and tissue lipids, circulating levels of cardiac and hepatic damage markers, and resulted in excretion of lipids through faeces. Also, the ARCE extract significantly attenuated alterations in the cardiac and hepatic antioxidants and lipid peroxidation, and histopathological changes in cardiac and hepatic tissue.

CONCLUSION

Thus, the present study provides the first scientific evidence for a protective role of ARCE against ATH diet-induced hypercholesterolaemia and cardiac and hepatic oxidative stress.

Sida rhomboidea.Roxb aqueous extract down-regulates in vivo expression of vascular cell adhesion molecules in atherogenic rats and inhibits in vitro macrophage differentiation and foam cell formation

The present study evaluates efficacy of Sida rhomboidea.Roxb (SR) leaves extract in ameliorating experimental atherosclerosis using in vitro and in vivo experimental models. Atherogenic (ATH) diet fed rats recorded significant increment in the serum total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), very LDL (VLDL), autoantibody against oxidized LDL (Ox-LDL), markers of LDL oxidation and decrement in high-density lipoprotein (HDL) along with increment in aortic TC and TG. The ex vivo LDL oxidation assay revealed an increased susceptibility of LDL isolated from ATH rats to undergo copper mediated oxidation. These set of changes were minimized by simultaneous co-supplementation of SR extract to ATH diet fed rats. Histopathology of aorta and immunolocalization studies recorded pronounced atheromatous plaque formation, vascular calcification, significant elastin derangements and higher expression of macrophage surface marker (F4/80), vascular cell adhesion molecule-1 (VCAM-1) and p-selectin in ATH rats. Whereas, ATH+SR rats depicted minimal evidence of atheromatous plaque formation, calcium deposition, distortion/defragmentation of elastin and accumulation of macrophages along with lowered expression of VCAM-1 and P-selectin compared to ATH rats. Further, monocyte to macrophage differentiation and in vitro foam cell formation were significantly attenuated in presence of SR extract. In conclusion, SR extract has the potency of controlling experimental atherosclerosis and can be used as promising herbal supplement in combating atherosclerosis.

Neonatal corticosterone programs for thrifty phenotype adult diabetic manifestations and oxidative stress: countering effect of melatonin as a deprogrammer

OBJECTIVE

The present study assesses the thrifty phenotype response of neonatal corticosterone programming to a diabetogenic challenge in adult rats and the role of melatonin as a deprogrammer.

METHODS

Neonates of both sexes, born of healthy male and female rats maintained under standard conditions of temperature and light, were separated and, equal number of pups was assigned to lactating mothers. Pups treated with either saline or corticosterone or, a combination of corticosterone and melatonin from postnatal day (PND) 2 to PND 14 and, at 120 days of age, six animals from each treatment group were rendered diabetic by alloxanization. Various serum and tissue parameters pertaining to glycaemic regulation, dyslipidemia, hepatic and renal distress and oxidative stress were analysed in adult rats of all groups.

RESULTS

The results indicate compromised feed efficiency, hyperglycaemia, hypoinsulinemia, decreased glycogen content, elevated serum and tissue lipids and serum markers of hepatic and renal stress, together with increased lipid peroxidation, and decreased levels of non-enzymatic and enzymatic antioxidants in corticosterone programmed diabetic animals than in the non-programmed diabetic rats. However, treatment with melatonin simultaneously prevented to a significant extent the alterations in carbohydrate and lipid metabolism and oxidative stress.

CONCLUSIONS

Melatonin is a potent deprogrammer of neonatal corticosterone programming effects and the adult thrifty phenotype alteration to a diabetogenic challenge.

Prior cadmium exposure improves glucoregulation in diabetic rats but exacerbates effects on metabolic dysregulation, oxidative stress, and hepatic and renal toxicity

The present study was taken up to assess the role of subchronic exposure to an environmentally relevant dosage of cadmium in type l diabetes. Female rats of the Wistar strain were treated with cadmium (5.12 mg/kg body weight) for 45 days. On day 46, rats were made diabetic by alloxan. After 7 days, diabetes (i.e., animals with serum glucose greater than 300 mg/dL) in the alloxanized animals was confirmed and further experiments were conducted for 15 days. Cadmium pretreatment showed disturbed glucose homeostasis with attendant changes in carbohydrate metabolism, coupled with decrease in food and water intake. Disturbance in carbohydrate metabolism was indicated by altered tissue metabolite load, as marked by a decrease in protein and glycogen contents and increased cholesterol store. Poor glucose clearance subsequent to a glucose challenge under the glucose tolerance test was observed in these animals (0.48/min in control vs. 0.13/min in Cd animals). There was a significantly lower glucose elevation rate in the insulin response test subsequent to an insulin-induced decrease in glucose level in Cd-exposed animals. Elevated oxidative stress was marked by increased lipid peroxidation, decreased antioxidant (both nonenzymatic and enzymatic) levels, and serum markers of hepatic and renal damage. Decreased corticosterone levels, together with increased E2 and reduced P4 levels, were some of the hallmark changes in the serum hormone profile of Cd-exposed animals. Overall, the present results are novel and interesting to open more investigations on animal models of type 1 diabetes with a history of previous Cd exposure.

Oreocnide integrifolia Flavonoids Augment Reprogramming for Islet Neogenesis and β-Cell Regeneration in Pancreatectomized BALB/c Mice

Agents which can either trigger proliferation of β-cells or induce neogenesis of β-cells from precursors would be of pivotal role in reversing diabetic manifestations. We examined the role of flavonoid rich fraction (FRF) of Oreocnide integrifolia leaves using a mice model of experimental regeneration. BALB/c mice were subjected to ~70% pancreatectomy (Px) and supplemented with FRF for 7, 14, and 21 days after pancreatectomy. Px animals displayed increased blood glucose levels and decreased insulin titres which were ameliorated by FRF supplementation. FRF-treated mice demonstrated prominent newly formed islets budding off from ducts and depicting increased BrdU incorporation. Additionally, transcripts levels of Ins1/2, Reg-3α/γ, Ngn-3, and Pdx-1 were upregulated during the initial 1 week. The present study provides evidence of a nutraceutical contributing to islet neogenesis from ductal cells as the mode of β-cell regeneration and a potential therapeutic for clinical trials in management of diabetic manifestations.

Melatonin supplementation therapy as a potent alternative to ERT in ovariectomized rats

AIM

To evaluate the efficacy of melatonin supplementation therapy as an alternative to estrogen replacement therapy in an ovariectomized rat model and to assess diabetogenic metabolic dysregulation caused by estrogen deficiency in postmenopausal individuals.

METHODS

Ovariectomized adult Wistar rats were treated with either estrogen/progesterone, melatonin or a combination of estrogen and melatonin. Body weight gain, feed efficiency, serum glucose, insulin, glucose tolerance and insulin response, serum and tissue lipids, tissue glycogen contents and activities of glycogen phosphorylase and glucose-6-phosphatase were analyzed in all the experimental groups.

RESULTS

Ovariectomized animals showed increased body weight gain, feed efficiency, fasting insulin resistance, greater area under curve for the glucose tolerance test, higher serum and tissue lipids and reduced glycogen content and insulin sensitivity. A low dose of melatonin was more efficient than estrogen in reversing all the ovariectomy-induced changes. The combination of estrogen + melatonin was found to be best in correcting glycemic dysregulation while high doses of melatonin could effectively regulate dyslipidemia.

CONCLUSION

The present study provides strong evidence for melatonin supplementation therapy to be more potent and effective in comparison to estrogen replacement therapy due to its single-handed ability to revert all the ovariectomy-induced changes. No reported side-effect or long-term effect of melatonin, against the known effects of estrogen replacement therapy, make it more attractive as a candidate to treat postmenopausal symptoms.

Antioxidant rich flavonoids from Oreocnide integrifolia enhance glucose uptake and insulin secretion and protects pancreatic β-cells from streptozotocin insult

BACKGROUND

Insulin deficiency is the prime basis of all diabetic manifestations and agents that can bring about insulin secretion would be of pivotal significance for cure of diabetes. To test this hypothesis, we carried out bioactivity guided fractionation of Oreocnide integrifolia (Urticaceae); a folklore plant consumed for ameliorating diabetic symptoms using experimental models.

METHODS

We carried out bioassay guided fractionation using RINmF and C2C12 cell line for glucose stimulated insulin secretion (GSIS) and glucose uptake potential of fractions. Further, the bioactive fraction was challenged for its GSIS in cultured mouse islets with basal (4.5 mM) and stimulated (16.7 mM) levels of glucose concentrations. The Flavonoid rich fraction (FRF) was exposed to 2 mM streptozotocin stress and the anti-ROS/RNS potential was evaluated. Additionally, the bioactive fraction was assessed for its antidiabetic and anti-apoptotic property in-vivo using multidose streptozotocin induced diabetes in BALB/c mice.

RESULTS

The results suggested FRF to be the most active fraction as assessed by GSIS in RINm5F cells and its ability for glucose uptake in C2C12 cells. FRF displayed significant potential in terms of increasing intracellular calcium and cAMP levels even in presence of a phosphodiesterase inhibitor, IBMX in cultured pancreatic islets. FRF depicted a dose-dependent reversal of all the cytotoxic manifestations except peroxynitrite and NO formation when subjected in-vitro along with STZ. Further scrutinization of FRF for its in-vivo antidiabetic property demonstrated improved glycemic indices and decreased pancreatic β-cell apoptosis.

CONCLUSIONS

Overall, the flavonoid mixture has shown to have significant insulin secretogogue, insulinomimetic and cytoprotective effects and can be evaluated for clinical trials as a therapeutant in the management of diabetic manifestations.

Clerodendron glandulosum.Coleb leaf extract attenuates in vitro macrophage differentiation and expression of VCAM-1 and P-selectin in thoracic aorta of atherogenic diet fed rats

Present inventory evaluates the anti-atherogenic potential of C. glandulosum.Coleb leaf extract (CG) using in vivo and in vitro experimental models. Serum markers of low density lipoprotein (LDL-C) oxidation, cholesterol, triglycerides, lipoproteins, auto-antibody titer, ex vivo LDL-C oxidation, LDL-C aggregation, aortic lipids, histopathological evaluations and immunolocalization of macrophage surface marker (F4/80), vascular cell adhesion molecule-1 (VCAM-1) and P-selectin were performed in CON [rats treated with single dose of saline (i.p.) and fed with laboratory chow], ATH [rats treated with single dose of vitamin D3 (600,000 IU, i.p) and fed with atherogenic diet] and ATH+CG [rats treated with single dose of vitamin D3 (600,000 IU, i.p.) and fed with atherogenic diet and simultaneously treated with 200 mg/kg CG extract, p.o.] for 8 weeks. CG extract supplementation to atherogenic diet fed rats significantly prevented increment in serum cholesterol, triglycerides, and lipoproteins, markers of LDL-C oxidation, auto-antibody titer and aortic lipids. Also, LDL-C isolated from ATH+CG rats recorded mimimal aggregation and susceptibility to undergo ex vivo LDL-C oxidation. Microscopic evaluation of thoracic aorta of ATH+CG rats reveled prevention of atheromatous plaque formation, accumulation of lipid laden macrophages, calcium deposition, distortion/defragmentation of elastin, accumulation of macrophages and, down regulation of cell adhesion molecules (VCAM-1 and P-selectin) expression. Further, in vitro monocyte to macrophage differentiation was significantly attenuated in presence of CG extract (200 µg/mL). It can be concluded from the present study that, CG extract is capable of controlling induction of experimental atherosclerosis and warrants further scrutiny at the clinical level as a possible therapeutic agent.

Plasticity changes in adult metabolic homeostasis and tissue oxidative stress: neonatal programming by corticosterone and melatonin as deprogrammer

OBJECTIVE

To evaluate the long-term plasticity changes induced by neonatal corticosterone programming on adult metabolic status and the deprogramming effect of melatonin.

METHODS

Male and female Wistar rats were maintained under standard conditions and when mated females delivered pups, neonates of both sexes were separated and equal number of pups was assigned to lactating mothers. Pups treated with saline, corticosterone or a combination of corticosterone and melatonin from PND 2 to PND 14, were maintained until 120 days of age. Various serum and tissue parameters pertaining to glycaemic regulation, dyslipidemia, hepatic and renal distress and oxidative stress were analyzed in adult rats.

RESULTS

Neonatal corticosterone exposure induced dyslipidemia, increased fed and fasting glucose levels, insulin resistance, lipid peroxidation, serum levels of insulin, corticosterone and hepatic and renal dysfunction markers and decreased the levels of enzymatic and non-enzymatic antioxidants, relatively more in males. Melatonin proved as an effective deprogrammer of corticosterone induced plasticity changes.

CONCLUSIONS

Neonatal corticosterone exposure induces long lasting effects on adult physiology and metabolism. Concurrent treatment with melatonin effectively deprograms the changes.

Sida rhomboidea. Roxb leaf extract down-regulates expression of PPARγ2 and leptin genes in high fat diet fed C57BL/6J Mice and retards in vitro 3T3L1 pre-adipocyte differentiation

Sida rhomboidea. Roxb leaf extract (SRLE) is being used by the populace of North-East India to alleviate symptoms of diabetes and obesity. We have previously reported its hypolipidemic and anti-diabetic properties. In this study, we report the effect of SRLE on (i) in vivo modulation of genes controlling high fat diet (HFD) induced obesity and (ii) in vitro 3T3L1 pre-adipocyte differentiation and leptin release. Supplementation with SRLE significantly prevented HFD induced increment in bodyweight, plasma lipids and leptin, visceral adiposity and adipocyte hypertrophy. Also, SRLE supplementation reduced food intake, down regulated PPARγ2, SREBP1c, FAS and LEP expressions and up-regulated CPT-1 in epididymal adipose tissue compared to obese mice. In vitro adipogenesis of 3T3L1 pre-adipocytes was significantly retarded in the presence of SRLE extract. Also decreased triglyceride accumulation, leptin release and glyceraldehyde-3-Phosphate dehydrogenase activity along with higher glycerol release without significant alteration of viability of 3T3L1 pre-adipocytes, was recorded. Our findings suggest that prevention of HFD induced visceral adiposity is primarily by down regulation of PPARγ2 and leptin gene expression coupled with attenuation of food intake in C57BL/6J mice. SRLE induced prevention of pre-adipocytes differentiation, and leptin release further substantiated these findings and scientifically validates the potential application of SRLE as a therapeutic agent against obesity.

Anti-obesity potential of Clerodendron glandulosum.Coleb leaf aqueous extract

ETHNOPHARMACOLOGICAL RELEVANCE

Clerodendron glandulosum.Coleb leaf aqueous extract (CG) is traditionally used by people of North-East India to alleviate symptoms of diabetes, obesity and hypertension. Previous study from our laboratory have documented anti-diabetic and anti-hypertensive properties of CG extract but, till date there are no pharmacological studies available on its anti-obesity potential. This inventory investigates the underlining molecular mechanism/s of CG induced regulation of in vivo HFD induced obesity and in vitro adipocyte differentiation.

AIM

To evaluate effects of CG extract on (i) expression of genes regulating visceral adiposity and (ii) in vitro adipocyte differentiation and LEP release.

MATERIALS AND METHODS

Body weight, lee index, plasma lipids and LEP, mRNA expression of PPARγ-2, SREBP1c, FAS, CPT-1 and LEP in epididymal adipose tissue of control and experimental groups were evaluated. Also, potential of CG extract on in vitro adipocyte differentiation and LEP release was assessed.

RESULTS

Supplementation of CG extract to HFD fed mice significantly prevented HFD induced increment in bodyweight, lee index, plasma lipids and LEP, visceral adiposity and adipocyte hypertrophy. Also, CG extract supplementation resulted in down regulation of PPARγ-2, SREBP1c, FAS and LEP expression along with up-regulation of CPT-1 in epididymal adipose tissue compared to HFD fed mice. In vitro study recorded significant anti-adipogenic effect of CG extract that resulted in decreased adipogenesis, TG accumulation, LEP release, G3PDH activity along with higher glycerol release without significantly altering viability of 3T3L1 pre-adipocytes.

CONCLUSIONS

Clerodendron glandulosum.Coleb extract prevents adipocyte differentiation and visceral adiposity by down regulation of PPARγ-2 related genes and Lep expression thus validating its traditional therapeutic use in controlling obesity.

Influence of Oreocnide integrifolia (Gaud.) Miq on IRS-1, Akt and Glut-4 in Fat-Fed C57BL/6J Type 2 Diabetes Mouse Model

Oreocnide integrifolia (OI) leaves are used as folklore medicine by the people of northeast India to alleviate diabetic symptoms. Preliminary studies revealed hypoglycemic and hypolipidemic potentials of the aqueous leaf extract. The present study was carried out to evaluate whether the OI extract induces insulin secretion in vivo and in vitro and also whether it is mediated through the insulin-signaling pathway. The experimental set-up consisted of three groups of C57BL/6J mice strain: (i) control animals fed with standard laboratory diet, (ii) diabetic animals fed with a high-fat diet for 24 weeks and (iii) extract-supplemented animals fed with 3% OI extract along with high-fat diet for 24 weeks. OI-extract supplementation lowered adiposity and plasma glucose and insulin levels. Immunoblot analysis of IRS-1, Akt and Glut-4 protein expressions in muscles of extract-supplemented animals revealed that glucoregulation was mediated through the insulin-signaling pathway. Moreover, immunostaining of pancreas revealed increased insulin immunopositive cells in OI-extract-treated animals. In addition, the insulin secretogogue ability of the OI extract was demonstrated when challenged with high glucose concentration using isolated pancreatic islets in vitro. Overall, the present study demonstrates the possible mechanism of glucoregulation of OI extract suggestive of its therapeutic potential for the management of diabetes mellitus.

Protective effect of Clerodendron glandulosum extract against experimentally induced metabolic syndrome in rats

CONTEXT

Metabolic syndrome (MetS) has become one of the major health burdens worldwide. To date, no single pharmacological agent has been developed to correct metabolic abnormalities associated with MetS. Use of indigenous medicinal plants as alternative medicines against MetS could be beneficial due to multiple therapeutic usage, easy availability, and relatively few side effects.

OBJECTIVE

To investigate the protective effect of Clerodendron glandulosum Coleb. (Verbenaceae) aqueous leaf extract (CgE) against experimentally induced MetS in rats.

METHODS

Changes in body weight, food and fluid intake, plasma glucose, insulin, fasting insulin resistance index (FIRI), plasma total lipid profile, free fatty acids (FFA), oral glucose tolerance test (OGTT), blood pressure and vascular reactivity have been investigated in various experimental groups.

RESULTS

Fructose+CgE groups recorded significant decrement (P <0.05) in plasma glucose, insulin, FIRI, total cholesterol, triglycerides, LDL, VLDL and FFA, whereas plasma HDL level was significantly increased (P <0.05) along with an efficient clearance of glucose during OGTT and lowered area under curve values. FRU+CgE groups also showed significantly decreased (P <0.05) mean arterial blood pressure along with decreased vasoconstriction and increased vasorelaxation in response to administration of various pharmacological agents. These results were comparable with metformin treated rats.

DISCUSSION

C. glandulosum leaf extract ameliorates experimentally induced MetS by improving dyslipidemia and insulin resistance.

CONCLUSION

This study provides the first pharmacological evidence for the protective role of C. glandulosum leaves against experimentally induced MetS. Thus, therapeutic use of C. glandulosum in controlling MetS is indicated.

Sida rhomboidea.Roxb leaf extract ameliorates gentamicin induced nephrotoxicity and renal dysfunction in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Sida rhomboidea.Roxb (SR) known as "Mahabala" in Ayurveda and marketed as "Shahadeyi" is used in ethnomedicine to treat ailments such as dysuria and urinary disorders.

AIM OF THE STUDY

To evaluate nephroprotective potential of SR against gentamicin (GM) induced nephrotoxicity and renal dysfunction.

MATERIALS AND METHODS

Nephrotoxicity was induced in rats with GM (100 mg/kg bodyweight (i.p.) for 8 days) and were treated with SR extract (200 and 400 mg/kg bodyweight (p.o.) for 8 days) or 0.5% carboxymethyl cellulose (vehicle). Plasma and urine urea and creatinine, renal enzymatic and non-enzymatic antioxidants along with lipid peroxidation were evaluated in various experimental groups.

RESULTS

GM treatment induced significant elevation (p<0.05) in plasma and urine urea, creatinine, renal lipid peroxidation along with significant decrement (p<0.05) in renal enzymatic and non-enzymatic antioxidants. SR treatment to GM treated rats (GM+SR) recorded significant decrement (p<0.05) in plasma and urine urea and creatinine, renal lipid peroxidation along with significant increment (p<0.05) in renal enzymatic and non-enzymatic antioxidants.

CONCLUSION

SR leaf extract ameliorates GM induced nephrotoxicity and renal dysfunction and thus validates its ethnomedicinal use.

Melatonin protects against alterations in hippocampal cholinergic system, trace metals and oxidative stress induced by gestational and lactational exposure to cadmium

Dietary exposure to cadmium, even at lower doses, can lead to free radical induced neurotoxicity, neurobehavioral changes and alteration in neurotransmitters. Such changes are likely to be more pronounced in the developing brain due to incompleteness of blood brain barrier (BBB). Hippocampus being the seat of intelligence has a role in learning and cognitive behavior and any damage to hippocampus during developmental stage is likely to result in neurodegenerative changes in later life. To this end, fetal and neonatal exposure to cadmium was induced by exposing pregnant dams of Swiss albino strain throughout the period of gestation and following parturition up till 5^th day post partum (pp) through drinking water (3ppm/animal/day). The neonates were sacrificed on day 6 pp and indices of oxidative stress, levels of trace elements and changes in cholinergic system were evaluated in the hippocampus. Increased lipid peroxidation, surge in reactive oxygen species (ROS), depressed antioxidant defense, increased accumulation of cadmium, differential alterations in trace elements and decreased activity of AChE were the features of cadmium toxicity. Simultaneous administration of melatonin to cadmium challenged animals offset these detrimental changes. The results suggest that melatonin co-administration can effectively protect against the adverse effects of cadmium on endogenous antioxidant status, changes in trace metal concentrations and compromised hippocampal cholinergic system.

Toxicological evaluation and hepatoprotective potential of Clerodendron glandulosum.Coleb leaf extract

This inventory evaluates toxicological effects and hepatoprotective potential of Clerodendron glandulosum.Coleb (CG) aqueous extract. Acute and subchronic toxicity tests were performed using Swiss albino mice as per the guideline of Organisation for Economic Cooperation and Development (OECD). Also, hepatoprotective potential of CG extract was examined in experimental model of carbon tetrachloride (CCl 4)-induced hepatotoxicity. Acute and subchronic toxicity tests revealed that CG extract is non-toxic and its median lethal dose (LD50) value is >5000 mg/kg bodyweight. Also, rats pretreated with CG extract followed by administration of CCl4 recorded significant decrement in plasma marker enzymes of hepatic damage, total bilirubin content and hepatic lipid peroxidation. While, hepatic reduced glutathione, ascorbic acid content, activity levels of superoxide and catalase and plasma total protein content were significantly increased. Microscopic examination of liver showed that pretreatment with CG extract prevented CCl4-induced hepatic damage in CG + CCl 4 group. CG extract has hepatoprotective potential by modulating activity levels of enzymes and metabolites governing liver function and by helping in maintaining cellular integrity of hepatocytes that is comparable with that of standard drug silymarin. CG extract exhibits potent hepatoprotective activity against CCl4-induced hepatic damage but does not exhibit any toxic manifestations.

Cardioprotective effect of Sida rhomboidea. Roxb extract against isoproterenol induced myocardial necrosis in rats

The present study investigates cardioprotective effect of Sida rhomboidea. Roxb (SR) extract on heart weight, plasma lipid profile, plasma marker enzymes, lipid peroxidation, endogenous enzymatic and non-enzymatic antioxidants and membrane bound ATPases against isoproterenol (IP) induced myocardial necrosis (MN) in rats. Rats treated with IP (85 mg/kg, s.c.) recorded significant (p<0.05) increment in heart weight, plasma lipid profile, plasma marker enzymes of cardiac damage, cardiac lipid peroxidation (LPO) and activity levels of Ca(+2) ATPase whereas there was significant (p<0.05) decrease in plasma HDL, cardiac endogenous enzymatic and non-enzymatic antioxidants, Na(+)-K(+) ATPase and Mg(+2) ATPase. Pre-treatment with SR extract (400 mg/kg per day, p.o.) for 30 consecutive days followed by IP injections on days 29th and 30th, showed significant (p<0.05) decrease in heart weight, plasma lipid profile, plasma marker enzymes of cardiac damage, cardiac lipid peroxidation, Ca(+2) ATPase and significant increase in plasma HDL, cardiac endogenous enzymatic and non-enzymatic antioxidants, Na(+)-K(+) ATPase and Mg(+2) ATPase compared to IP treated group. Hence, this study is the first scientific report on cardioprotective effect of SR against IP induced MN in rats.

Neonatal hypothyroidism-induced changes in rat testis size, dependence on temperature

OBJECTIVE

Effects of transient neonatal hypothyroidism (HPOT) on adult testis size and serum hormone profiles were evaluated in the Charles foster strain of rats, maintained under the temperature of 21 degrees C (HPOTL) or of 34 degrees C (HPOTH).

METHODS

Hypothyroidism was induced in suckling pups in preweanling period (1-21 days), by administering 0.1% 6-propyl-2-thiouracil in drinking water to mothers. Body mass and testis characteristics, the steroidogenic potential [measured by histochemical localization of 3alpha-, 3beta- and 17beta-hydroxysteroid dehydrogenases (HSDHs)] and serum concentrations of thyroid-stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), luteinizing hormone (LH), testosterone (T) and corticosterone (Cort) were evaluated on the 35th, 45th, 60th and 90th day of age.

RESULTS

The HPOTH rats showed lower testis masses, while the HPOTL rats showed higher testis masses and lower body masses after 90 days. Histologically, the testes of the HPOTH rats demonstrated increased germ cell degeneration after 35 and 45 days and reduced tubular size, germ cell numbers and sperm density after 90 days. In contrast, the testes of the HPOTL rats showed reduced tubular diameters after 35 and 45 days, and increased tubular diameters, germ cell numbers and sperm density after 90 days. Serum TSH, T3, T4, LH and T concentrations and 3beta- and 17beta-HSDH activities were reduced in both groups of the HPOT rats after 35 and 45 days. Intratubular steroidogenesis and a prominent triangle up5 pathway were also found in the HPOT animals.

CONCLUSION

The temperature has a definite influence on the thyroid hormone action, postnatal growth and function of rat testes.

Effect of short photoperiod on organ growth kinetics and serum hormone profile in pullets of domestic fowl, Gallus gallus domesticus

Effect of short photoperiod (SP; LD 6:18) treatment on serum hormone profile and growth rate of adrenal, thyroid, ovary, oviduct, liver and lymphoid organ was studied in rearing pullets (RIR breed) of 1 to day 90 old. Body weight and growth index of SP pullets were lesser as compared to pullets reared under LD 12:12. Except for ovary (recorded marginal increment), weights and growth indices of thyroid, adrenal and oviduct decreased under SP. Weight of liver and lymphoid organs was higher at 30 and 90 days, in SP pullets as compared to LD 12:12. Histometric data suggested that the transition from small to big follicles was slow in ovary of SP pullets, and also reduced follicular atresia was noted in SP pullets. Except for higher corticosterone level at 30 days and higher progesterone level at 30 and 60 days, relative levels of all the hormones at all other ages were lower in SP pullets. In general, the present observations suggested intraovarian changes in pullets exposed to SP.

Effect of dexamethasone and corticosterone on activity levels of ATPase, phosphomonoesterases and phosphodiesterase in liver, muscle and testis of post-hatched White Leghorn chicks

Muscle ATPase activity did not show much change with any of the treatments, while hepatic total and Ca(2+)-Mg(2+)-ATPase activities were decreased with low dose of dexamethasone (DXM(L) and enzyme activity in general was increased with both high dose of DXM(H) and corticosterone. Total and Ca(2+)-Mg(2+)-ATPases were increased in testis of corticosterone treated chicks. Acid phosphatase activity of testis was increased with DXM(H) and decreased with DXM(L) while the enzyme activity in all the three tissues was increased with corticosterone. Muscle alkaline phosphatase activity was decreased with DXM treatments while that of testis was decreased with both DXM(H) and corticosterone treatments. Hepatic PDE activity was decreased with DXM and increased with corticosterone while muscle PDE activity was decreased under both DXM(H) and corticosterone treatments. The results suggest that both hypo. and hypercorticalism can induce tissue specific differential alterations in phosphomonoesterases, ATPases and PDE during early phases of post-natal development of chicks.

Local and systemic alterations in cyclic 3',5' AMP phosphodiesterase activity in relation to tail regeneration under hypothyroidism and T4 replacement in the lizard, Mabuya carinata

To establish the relationship between thyroid hormone and cyclic Adenosine monophosphate (cAMP) during lacertilian tail regeneration, cAMP phosphodiesterase, the hydrolytic enzyme of cAMP, was assayed in the tail regenerate, liver, and skeletal muscle of control (group A), chemically thyroidectomized (group B), and thyroidectomized and T4-replaced (group C) animals during various periods of tail regeneration. Enzyme activity was elevated in all three tissues of group B animals. Animals of group C showed an intermediate level of enzyme activity between controls (group A) and experimental animals (group B). These observations suggest a possible regulatory role of thyroxine in maintaining optimum levels of phosphodiesterase. The retardation in regeneration observable in the hypothyroid group of animals may be correlated with low levels of tissue cAMP. However, the operation of other influencing factors on phosphodiesterase during regeneration can be surmised from the observed tendency to exhibit similar patterns of phase-specific modulations in enzyme activity. Our observations are discussed in terms of phase-specific involvement of cAMP in regeneration, as well as its role in other metabolic aspects and the possible mode of indirect control exerted by thyroxine on lacertilian tail regeneration.

Dexamethasone-induced alterations in glucose tolerance and, insulin, glucagon and adrenaline responses during the first month in White Leghorn chicks

1. Alterations in glucose tolerance and, insulin, glucagon and adrenaline responses in dexamethasone (DXM)-treated (induced hypocorticalism) chicks have been evaluated chronologically during the first month of development of White Leghorn chicks. 2. Alterations in glucose tolerance and, insulin resistance and glucagon and adrenaline responses in dexamethasonised chicks were recorded. Control chicks too displayed differential glucose tolerance and, insulin, glucagon and adrenaline responses on a chronological basis. 3. The observations suggest increased insulin and adrenaline sensitivity in the first fortnight and gradually increasing glucagon response in the second fortnight in neonatal chicks. 4. Furthermore, increased insulin sensitivity and attenuated glucagon responsiveness was also associated with DXM-induced hypocorticalism.

Roles of adrenal and gonadal steroids and season in uropygial gland function in male pigeons, Columba livia

To gauge the relative regulative roles of adrenal, gonadal, and thyroid hormones on uropygial gland of male adult pigeons, morphometric, histological, and histochemical observations have been made on a seasonal basis in normal as well as experimentally manipulated birds. Normal birds showed a parallel adrenal-gonadal-uropygial relationship and inverse adrenal-thyroid, thyroid-gonadal, and thyroid-uropygial relationships. Induced hypocorticalism by dexamethasone in the breeding season and hypercorticalism by ACTH or corticosterone treatment in the nonbreeding season were marked by inhibitory and stimulatory changes respectively in the uropygial gland and testis and by inverse thyroid activity. Further, cyproterone acetate treatment in the breeding season completely suppressed testicular functions and increased thyroid activity without affecting either adrenal or uropygial weight, structure, and functions. Based on the observations it is concluded that adrenal steroids are principally involved in regulating the uropygial gland while the gonadal steroids are involved in qualitative aspects of secretion during the breeding phase and thyroid hormones in maintaining the general metabolic profile.

Effect of exogenous dexamethasone and corticosterone on weight gain and organ growth in post-hatched white Leghorn chicks

Induced chronic hypocorticalism by dexamethasone (DXM) and hypercorticalism by corticosterone (CORT) retarded body weight gain as well as the growth of spleen, bursa, liver, kidney and pancreas during the first month of development in male leghorn chicks. Adrenal weight was reduced by DXM and increased by CORT. Correspondingly, there were histological regressive changes in the cortex with a decreased cortico-medullary ratio with DXM treatment, while a reverse trend was there with CORT treatment. However, an increase in weight of testis and better organization of seminiferous cords and interstitium was observed in DXM treated chicks, and there was a decrease in weight and poor histological organization in CORT treated chicks. Both DXM and CORT induced stimulatory changes in thyroid denoted by increased epithelial cell height and decreased colloidal content. These observations indicate that corticosteroids have definite influence on post-hatched growth and maturation of chicks.

Alterations in carbohydrate metabolism by exogenous dexamethasone and corticosterone in post-hatched White Leghorn chicks

1. Alterations in carbohydrate metabolism in terms of tissue glycogen contents, phosphorylase (EC 2.4.1.1) activity, hepatic glucose-6-phosphatase (6-6-Pase: EC 3.1.3.9) activity and blood glucose have been evaluated in 30-d-old White Leghorn chicks under induced chronic hypocorticalism (by dexamethasone: DXM) and hypercorticalism (by corticosterone: CORT). 2. DXM treatment showed increased tissue glycogen contents and hypoglycaemia with decreased phosphorylase activity while CORT treatment produced a reverse set of changes. 3. Both steroid treatments increased hepatic G-6-Pase activity. These observations have been taken to indicate a definite role for glucocorticoids in regulating carbohydrate metabolism in neonatal chicks. 4. It is suggested that hypo- or hyper-corticalism could influence carbohydrate metabolism by affecting the secretory/activity ratio of pancreatic hormones.

In vitro influence of hormones on transport of glucose and glycogen in liver and muscle of pinealectomised pigeons, Columba livia Gmellin

To substantiate the increased peripheral utilization of blood glucose by pineal in wild pigeons, an in vitro study on the ability of liver and muscle slices of intact and pinealectomised wild pigeons (C. livia) in terms of uptake and release of glucose, and deposition and depletion of glycogen, in presence of insulin, acetylcholine, glucagon and adrenaline has been undertaken. A total insensitivity of liver and muscle of pinealectomised birds for glycogen deposition and insensitivity of liver for glucose uptake has been observed. Increased glucose release from liver in response to adrenalin has been observed. The results are discussed in terms of involvement of pineal in metabolic regulation associated with breeding activities.

Dopamine antagonist speeds up tail regeneration in lizards exposed to continuous darkness: evidence for prolactin involvement

In earlier studies, we demonstrated that continuous light (LL:LD, 24:0) stimulated tail regeneration whereas continuous darkness (DD:LD, 0:24) and pinealectomy depressed the same in the Gekkonid lizard, Hemidactylus flaviviridis, and, furthermore, exogenous prolactin significantly enhanced the regeneration process in lizards kept in 0:24 LD. However, the regeneration process in animals exposed to 24:0 LD was unaffected by the dopamine agonist, bromocriptine. This study with pimozide, an antipsychotic drug, and a potent dopamine receptor antagonist was conducted to ascertain whether the dopaminergic regulation of prolactin release is operative in lizards, as in mammals, and to provide further evidence for prolactin involvement in regenerative growth. Once daily intraperitoneal injection of 50 micrograms/kg pimozide to H. flaviviridis, 5 days prior to tail autotomy and 50 days thereafter, stimulated the regeneration process in lizards exposed to 0:24 LD. The initiation of regeneration, the total length of new growth (regenerate) produced by Day 50, and the total percentage replacement of the lost (autotomized) tails at the end of 50 days of experimentation were all significantly enhanced in pimozide-treated animals as compared with their counterparts injected with 0.6% sterile saline; in fact, better than saline-injected controls exposed to 24:0 LD of 638 lux intensity. The daily growth rate was also enhanced in pimozide-treated lizards. Interestingly, the pattern of regeneration as well as the final regenerate of pimozide-treated lizards were similar to those observed earlier in ovine prolactin-treated animals exposed to similar experimental photoperiodic schedules.(ABSTRACT TRUNCATED AT 250 WORDS)

Is the pineal involved in the stimulatory influence of prolactin on tail regeneration in lizards? Studies with exogenous prolactin in lizards exposed to continuous darkness

We have recently demonstrated that continuous light stimulates tail regeneration in the gekkonid lizard, Hemidactylus flaviviridis, whereas continuous darkness and pinealectomy depress regeneration. As a sequel to this observation, the effect of exogenous ovine prolactin (oPRL) on tail regeneration in normal (NL) and pinealectomized (PX) Hemidactylus exposed to continuous darkness (L:D 0:24) during the monsoon season was investigated. Once-daily intraperitoneal (ip) injections of 500 micrograms/kg oPRL were administered to a group of NL lizards, a group of PX lizards, and a group of sham-PX (sPX) lizards, 5 days prior to tail autotomy and 50 days afterward. Three groups--PX, sPX, and NL animals--served as the controls and received once-daily ip injections of 0.6% saline. Our observations show that initiation of regeneration, daily growth rate, total length of new growth (regenerate) at the end of regeneration, and total percentage replacement of lost (autotomized) tail were all significantly enhanced in oPRL-treated NL lizards as compared with their saline-treated (NL, PX, and sPX) and oPRL-treated (PX and sPX) counterparts. It is suggested that PRL may be the active factor that speeds up the rate of tail regeneration in lacertilians. The role of the pineal organ in vertebrate photoreception and the possibility that in Hemidactylus the presence of an intact pineal is somehow linked with the favorable influence of PRL on tail regeneration are discussed.

Parachlorophenylalanine retards tail regeneration in the gekkonid lizard Hemidactylus flaviviridis exposed to continuous light

Parachlorophenylalanine (p-CPA) was used for chemical pinealectomy in a study of tail regeneration in the gekkonid lizard, Hemidactylus flaviviridis. Two doses of p-CPA (200 or 400 micrograms kg-1 body mass) were injected into two groups of lizards (5 days prior to and 30 days after caudal autotomy) exposed to continuous light of 2500 lx intensity during the summer season (March-May). Our observations show that the initiation of regeneration, the daily growth rate, the total length of new growth (regenerate) produced, and the total percentage replacement of the lost (autotomized) tails 30 days after autotomy were all significantly less with 400 micrograms kg-1 and insignificantly less with 200 micrograms kg-1 of p-CPA than in the control group of animals. The results may indicate that the effect of the drug p-CPA, an agent employed for chemical pinealectomy, on tail regeneration in H. flaviviridis is dose-dependent and that p-CPA at the high dose of 400 micrograms kg-1 has a similar retardation effect to that of complete pineal ablation. The role of the pineal in photoperiodic photoreception, and the effect of p-CPA on serotonin-melatonin biosynthesis and the consequent effects on tail regeneration, are discussed.