Effects of melatonin on biochemical factors and food and water consumption in diabetic rats

Evaluating the effectiveness of melatonin in reducing the risk of foot ulcers in diabetic patients

Objectives

Diabetes and its complications, as a major health concern, are associated with morbidity and mortality around the world. One of these complications is diabetic foot ulcer. Factors such as hyperglycemia, neuropathy, vascular damage and impaired immune system can cause foot ulcers. The present review aims to study the potential effects of melatonin, the main product of pineal glands, on diabetic foot ulcers.

Methods

A narrative review was performed using present literature in an attempt to identify the different aspects of melatonin's impact on diabetic foot ulcers by searching related keywords in electronic databases without any restriction.

Results

This review shows that, melatonin has anti-diabetic effects. It is effective in reducing the risk of hyperglycemia, neuropathy, vascular damage and immune system impairment in diabetic patients. By reducing these complications with melatonin, correspondingly, the incidence of diabetic foot ulcers may also decrease in these patients.

Conclusions

The results of this study indicate promising properties of melatonin while dealing with diabetic foot ulcers and their common underlying conditions, but still, it needs to be investigated more in future studies.

Co-administration of exercise training and melatonin on the function of diabetic heart tissue: a systematic review and meta-analysis of rodent models

PURPOSE

Diabetes mellitus (DM), a hyperglycemic condition, occurs due to the failure of insulin secretion and resistance. This study investigated the combined effects of exercise training and melatonin (Mel) on the function of heart tissue in diabetic rodent models.

METHODS

A systematic search was conducted in Embase, ProQuest, Cochrane library, Clinicaltrial.gov, WHO, Google Scholar, PubMed, Ovid, Scopus, Web of Science, Ongoing Trials Registers, and Conference Proceedings in July 2022 with no limit of date or language. All trials associated with the effect of Mel and exercise in diabetic rodent models were included. Of the 962 relevant publications, 58 studies met our inclusion criteria as follows; Mel and type 1 DM (16 studies), Mel and type 2 DM (6 studies), exercise and type 1 DM (24 studies), and exercise and type 2 DM (12 studies). Meta-analysis of the data was done using the Mantel Haenszel method.

RESULTS

In most of these studies, antioxidant status and oxidative stress, inflammatory response, apoptosis rate, lipid profiles, and glucose levels were monitored in diabetic heart tissue. According to our findings, both Mel and exercise can improve antioxidant capacity by activating antioxidant enzymes compared to the control diabetic groups (p < 0.05). The levels of pro-inflammatory cytokines, especially TNF-α were reduced in diabetic rodents after being treated with Mel and exercise. Apoptotic changes were diminished in diabetic rodents subjected to the Mel regime and exercise in which p53 levels and the activity of Caspases reached near normal levels (p < 0.05). Based on the data, both Mel and exercise can change the lipid profile in diabetic rodents, especially rats, and close it to near-to-control levels.

CONCLUSION

These data showed that exercise and Mel can reduce the harmful effects of diabetic conditions on the heart through the regulation of lipid profile, antioxidant capacity, apoptosis, and inflammation.

Melatonin protects against body weight gain induced by sleep deprivation in mice

Sleep deprivation is an epidemic phenomenon in modern society. Lack of sleep has been shown to result in metabolic and endocrine disorders that predispose to obesity and other chronic metabolic diseases. Melatonin is a sleep-related neurohormone and affected by the circadian rhythm and light/dark cycles. Melatonin has recently been used to ameliorate diet-induced or night light-induced energy metabolic imbalance. However, the effect of melatonin on sleep deprivation-induced obesity has been poorly characterized. This study focuses on the protective effects of melatonin on lipid metabolism and body weight homeostasis in sleep-deprived mice. Mice subjected to sleep deprivation had significantly decreased plasma melatonin content and increased food intake and body weight gain compared to that of control. Meanwhile, the transcription factor PPARγ protein in liver increased, but there were no significant changes in hepatic circadian proteins BMAL1 and REV-ERBα after 10 consecutive days of sleep deprivation. Moreover, melatonin supplementation increased liver AMPKα/PPARα signaling pathway activity, which leads to lipid catabolism and reduced fat accumulation. These findings suggested that melatonin may be a potential agent for protecting against sleep deprivation-induced obesity.

Studies on Bioactive Components of Red Ginseng by UHPLC-MS and Its Effect on Lipid Metabolism of Type 2 Diabetes Mellitus

Objectives

Red ginseng is a processed product of Panax ginseng C.A. Meyer, which is one of the widely used medicinal and edible herbs for the treatment of type 2 diabetes mellitus (T2DM). Ginsenosides are its main pharmacologically active ingredient. This study aims to clarify the material basis of total ginsenosides of red ginseng (RGW) and verify the activity of RGW in treating lipid metabolism disorders caused by T2DM.

Methods

An ultrahigh performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UHPLC-Q-TOF-MS) technology was applied to quantitatively analyze RGW. A T2DM rat model was established to verify the activity of RGW in treating lipid metabolism disorders caused by diabetes. First, the changes in diabetes-related parameters were observed, then the biochemical parameters of the rat serum and liver were measured, and finally, the pathological sections of the rat liver were observed, and the content of short-chain fatty acids in stools was measured. The in vitro activity of RGW was verified by fatty degenerated HepG2 cells.

Results

A total of 10 ginsenosides were identified and quantitatively analyzed in RGW. Experimental results demonstrated that RGW can improve lipid metabolism disorders. RGW significantly reduced the fasting blood glucose and TG and TC levels in T2DM rats, and hepatic steatosis was significantly ameliorated. In vitro experiments by RGW treatment also significantly attenuated lipid deposition in HepG2 cells. RGW upregulated the content of 5 short-chain fatty acids in rat stools, which are related to lipid oxidation and liver gluconeogenesis.

Conclusion

The total RGW were quantitatively analyzed by UHPLC-MS, and its effect on lipid metabolism of T2DM was studied. The experiment demonstrated that red ginseng can regulate lipid metabolism and improve lipid deposition, which provides a promising development for red ginseng as a functional food.

Kolaviron attenuates cardiovascular injury in fructose-streptozotocin induced type-2 diabetic male rats by reducing oxidative stress, inflammation, and improving cardiovascular risk markers

The prevalence of cardiovascular disease among type-2 diabetic patients has become a source of major concern world over. This study explored the protective effect of kolaviron, a bioflavonoid, against oxidative cardiovascular injury in fructose- streptozotocin-induced type 2 diabetic male Sprague Dawley rats. After acclimatization, induction, and confirmation of type-2 diabetes, kolaviron was administered for 28days, after which the animals were anesthetized with Isofor and euthanized. Blood from each rat were collected, and blood samples were then centrifuged for serum and plasma. Cardiac troponin I (cTnI), creatine kinase myocardial band (CK-MB), Creatine phosphokinase (CK), and insulin levels were immediately determined in serum, while remaining samples (serum, plasma, and organs) were stored in the bio-freezer at - 80 °C and 10% formalin for enzyme-link immunosorbent assay (ELISA), biochemical, molecular, and histopathological studies. The results show that type-2 diabetes induction with fructose and streptozotocin led to increased blood glucose levels, decreased insulin levels and cardiac antioxidant enzyme activities, increased malondialdehyde levels, cardiac biomarkers and pro-inflammatory cytokines levels, resulted in abnormal lipid profile, increased blood pressure and angiotensin-converting enzyme (ACE) activity, and decreased plasma endothelial nitric oxide synthase (eNOS) concentration. The histopathological examination of the cardiac tissue revealed severe lesion, hypertrophy, and myofibrils degeneration. However, administration of kolaviron for 28days remarkably improved these conditions. Hence the result from the study validates the potency of kolaviron, and suggests it could serve as an alternative to existing remedy in ameliorating or protecting against cardiovascular injury in type-2 diabetes.

Bee Pollen Polysaccharide From Rosa rugosa Thunb. (Rosaceae) Promotes Pancreatic β-Cell Proliferation and Insulin Secretion

Insufficient pancreatic β-cell or insulin-producing β-cell are implicated in all types of diabetes mellitus. Our previous studies showed bee pollen polysaccharide RBPP-P improves insulin resistance in type 2 diabetic mice by inhibiting liver fat deposition. However, its potential of regulating β-cell function and integrity is not fully known. Herein, we observed that β-cell proliferation (n = 10), insulin synthesis (n = 5, p = 0.01684) and insulin incretion (n = 5, p = 0.02115) were intensely activated in MIN6 cells when treatment with RBPP-P. In alloxan-induced diabetic mice, oral administration of RBPP-P (n = 10) effectively decreased the blood glucose (p = 0.0326), drink intake (p < 0.001) and urine (p < 0.001). It directly stimulated phosphorylation of p38 (p = 0.00439), ERK (p = 0.02951) and AKT (p = 0.0072) to maintain the islet function and mass. Thus, our data suggest that RBPP-P is a natural compound to regulate β-cell proliferation and function, indicating it might have therapeutic potential against type 1 diabetes.

The protective effect of hydrogen-rich water on rats with type 2 diabetes mellitus

The hydrogen-rich water (HW) has been reported to possess a beneficial role in patients with diabetes. However, a systemic evaluation with an appropriate animal model is necessary to reveal its mechanisms and efficacy. Herein, the protective effects of drinking HW on lipid and glucose metabolism, oxidative stress, and inflammation in type 2 diabetes mellitus (T2DM) rats were investigated. The well-modeled T2DM rats (induced by high-fat diet combined with low-dose streptozotocin (STZ) injection) were divided into two groups (n ≥ 15 of each): fed a high-fat diet and drinking distilled water or HW at a constant concentration above 1.0 ppm; normal rats were used as control group (n ≥ 10): fed a regular diet and drinking distilled water. Several biomarkers of lipid and glucose metabolism, oxidative stress ,and inflammation were evaluated after drinking distilled water or HW for 3 weeks. The effect of HW on liver, kidney, and spleen of T2DM rats was also analyzed by HE and Oil Red O staining. The results showed that drinking HW suppressed the increase in glucose, total cholesterol, oxidative stress, and inflammation. Moreover, HW also ameliorates hyperglycemia-induced liver, kidney, and spleen dysfunction. Overall, this study indicates that patients with T2DM may be able to improve their condition by supplementing HW as daily drinking water.

Melatonin protects the heart and pancreas by improving glucose homeostasis, oxidative stress, inflammation and apoptosis in T2DM-induced rats

Cardiomyopathy and pancreatic injury are health issues associated with type 2 diabetes mellitus (T2DM) and are characterized by elevated oxidative stress, inflammation and apoptosis. Melatonin (MLT) is a hormone with multifunctional antioxidant activity. The protective effects of MLT on the heart and pancreas during the early development of diabetic cardiomyopathy and pancreatic injury were investigated in male Wistar rats with T2DM. MLT (10 mg/kg) was administered daily by gavage for 15 days after diabetic induction. Treatment of diabetic rats with MLT significantly normalized the levels of serum glucose, HbA1-c, and the lipid profile and improved the insulin levels and insulin resistance compared with diabetic rats, affirming its antidiabetic effect. MLT significantly prevented the development of oxidative stress and sustained the levels of glutathione and glutathione peroxidase activity in the heart and pancreas of diabetic animals, indicating its antioxidant capacity. Additionally, MLT prevented the increase in proinflammatory cytokines and expression of Bax, caspase-3 and P53. Furthermore, MLT enhanced the anti-inflammatory cytokine IL-10 and antiapoptotic protein Bcl-2. MLT controlled the levels of troponin T and creatine kinase-MB and lactate dehydrogenase activity, indicating its anti-inflammatory and antiapoptotic effects. Histological examinations confirmed the protective effects of MLT on T2DM-induced injury in the myocardium, pancreas and islets of Langerhans. In conclusion, the protective effects of melatonin on the heart and pancreas during the early development of T2DM are attributed to its antihyperglycemic, antilipidemic and antioxidant influences as well as its remarkable anti-inflammatory and antiapoptotic properties.

Removal of melatonin receptor type 1 signalling induces dyslipidaemia and hormonal changes in mice subjected to environmental circadian disruption

Background

Melatonin is a hormone secreted by the pineal gland in a circadian rhythmic manner with peak synthesis at night. Melatonin signalling was suggested to play a critical role in metabolism during the circadian disruption.

Methods

Melatonin-proficient (C3H-f+/+ or WT) and melatonin receptor type 1 knockout (MT1 KO) male and female mice were phase-advanced (6 hours) once a week for 6 weeks. Every week, we measured weight, food intake and basal glucose levels. At the end of the experiment, we sacrificed the animals and measured the blood's plasma for lipids profile (total lipids, phospholipids, triglycerides and total cholesterol), metabolic hormones profiles (ghrelin, leptin, insulin, glucagon, glucagon-like-peptide and resistin) and the body composition.

Results

Environmental circadian disruption (ECD) did not produce any significant effects in C3H-f+/+, while it increased lipids profile in MT1 KO with the significant increase observed in total lipids and triglycerides. For metabolic hormones profile, ECD decreased plasma ghrelin and increased plasma insulin in MT1 KO females. Under control condition, MT1 KO females have significantly different body weight, fat mass, total lipids and total cholesterol than the control C3H-f+/+ females.

Conclusion

Our data show that melatonin-proficient mice are not affected by ECD. When the MT1 receptors are removed, ECD induced dyslipidaemia in males and females with females experiencing the most adverse effect. Overall, our data demonstrate that MT1 signalling is an essential modulator of lipid and metabolic homeostasis during ECD.

Hypoglycemic, antidyslipidemic and antioxydant effects of Vitellaria paradoxa barks extract on high-fat diet and streptozotocin-induced type 2 diabetes rats

Backgroud

Vitellaria paradoxa is a plant belonging to the Sapotaceae family and used in traditional medicine in the treatment of diabetes mellitus. The aim of this work was to evaluate the hypoglycemic, antidyslipidemic and antioxidant effects of V. paradoxa on type 2 diabetic rats.

Methods

To induce type 2 diabetes mellitus (T2DM), animals were fed a high-fat diet for 4 weeks followed by an intraperitoneal injection of 35 mg/kg of streptozotocin. Diabetic rats were divided into groups and treated for 28 days with V. paradoxa extract (AEVP) at doses of 125, 250 and 500 mg/kg. Body weight, urine volume, food and water consumption were assessed at the start and end of treatment. The glucose tolerance test was performed on the last day of treatment. Blood samples were taken for the assay of biochemical parameters, organs (kidneys and liver) for markers of oxidative stress and pancreas for histological sections.

Results

AEVP (250 and 500 mg/kg) improved the drop in body weight, polyphagia, polydipsia and polyuria in diabetic rats. AEVP significantly reduced the concentrations of glucose, total cholesterol, triacylglycerol, urea, creatinine, activities of transaminases, and increased the levels of high density lipoprotein cholesterol and serum insulin. AEVP resulted in a decrease in malondialdehyde levels and an increase in catalase and superoxide dismutase activities. An increase in the size and number of islets in the pancreas has also been observed after administration of the extract.

Conclusion

AEVP has antidiabetic, antidyslipidemic and antioxidant properties, thus confirming its traditional use for the treatment of diabetes. These effects could be due to the presence of phytoconstituents, phenols and flavonoids presents in the plant extract.

Dietary Melatonin Protects Against Behavioural, Metabolic, Oxidative, and Organ Morphological Changes in Mice that are Fed High-Fat, High- Sugar Diet

BACKGROUND

Metabolic syndrome is a complex pattern of disorders that occur jointly and is associated with an increased risk of cardiovascular and cerebrovascular disease. Therefore the need for more-efficient options of treatment has become imperative.

OBJECTIVE

This study examined the effect of dietary-melatonin in the management of behavioural, metabolic, antioxidant, and organ changes due to high-fat/high-sugar (HFHS) diet-induced metabolic syndrome in mice.

METHODS

Mice were randomly assigned into five groups of ten animals each. Groups were normal control [fed standard diet (SD)], HFHS control, and 3 groups of melatonin incorporated into HFHS at 2.5, 5, and 10 mg/kg of feed. Mice were fed for seven weeks, and body weight was assessed weekly. Open-field behaviours, radial-arm, and Y-maze spatial memory were scored at the end of the experimental period. Twenty-four hours after the last behavioural test, blood was taken for estimation of blood glucose levels after an overnight fast. Animals were then euthanised, and blood was taken for estimation of plasma insulin, leptin, and adiponectin levels, and serum lipid profile. The liver, kidneys, and brain were excised and processed for general histology, while homogenates of the liver and whole brain were used to assess oxidative stress parameters.

RESULTS

Results showed that dietary melatonin (compared to HFHS diet) was associated with a decrease in body weight, food intake, and novelty-induced behaviours; and an increase in spatial-working memory scores. A decrease in glucose, insulin, leptin, and malondialdehyde levels; and an increase in adiponectin levels and superoxide dismutase activity were also observed. Histomorphological/ histomorphometric examination revealed evidence of organ injury with HFHS diet, and varying degrees of amelioration with melatonin-supplemented diet.

CONCLUSION

In conclusion, dietary melatonin supplementation may have beneficial effects in the management of the metabolic syndrome.

Melatonin modulates inflammatory mediators and improves olanzapine-induced hepatic steatosis in rat model of schizophrenia

BACKGROUND

Melatonin (Mel) has lower levels and can be used as monotherapy in schizophrenia. Mel alleviated liver steatosis induced by atypical antipsychotics.

GOALS

To investigate Mel effect as monotherapy and addon treatment on ketamine-induced behavioral changes in rat schizophrenia model and olanzapine (Ola)-induced metabolic derangement.

METHODS

24 male rats divided into four groups; C: control; O: Ola; OM: Ola plus Mel and M: Mel. All groups treated orally daily for 25 days. We measured activities of daily life (ADL) and rat performance in radial arm water maze (RAWM) before and after ketamine (Ket) injection, serum level of liver enzymes, lipoproteins, sugar, inflammatory markers and liver histopathology.

RESULTS

Ket significantly reduced burrowing and hoarding behavior, increased working memory errors (WME) and time to reach target (TRT). Ola antagonized the deleterious effects of Ket on ADL, WME and TRT. Mel monotherapy significantly reduced burrowing and doesn't affect hoarding, WME or TRT in RAWM. Significant rise in ALT, AST, IL-1 beta, IL-6, IL-10, TNF-alpha, LDL, TGs and hepatic steatosis score (HSS) in O compared to C group. Co administration of Mel significantly decreased ALT, AST, IL-1 beta, IL-6 and TNF alpha. Insignificant difference in IL-10, TGs or LDL and significant improvement in HSS in OM compared to O group. Insignificant change in HDL or blood sugar in both O and OM groups compared to C group detected.

CONCLUSION

Although ineffective as monotherapy, Mel co administration provides promising natural way to improve Ola-induced hepatic derangement in psychotic disorders.

Stability of a type 2 diabetes rat model induced by high-fat diet feeding with low-dose streptozotocin injection

OBJECTIVE

The present study aims at determining the stability of a popular type 2 diabetes rat model induced by a high-fat diet combined with a low-dose streptozotocin injection.

METHODS

Wistar rats were fed with a high-fat diet for 8 weeks followed by a one-time injection of 25 or 35 mg/kg streptozotocin to induce type 2 diabetes. Then the diabetic rats were fed with regular diet/high-fat diet for 4 weeks. Changes in biochemical parameters were monitored during the 4 weeks.

RESULTS

All the rats developed more severe dyslipidemia and hepatic dysfunction after streptozotocin injection. The features of 35 mg/kg streptozotocin rats more resembled type 1 diabetes with decreased body weight and blood insulin. Rats with 25 mg/kg streptozotocin followed by normal diet feeding showed normalized blood glucose level and pancreatic structure, indicating that normal diet might help recovery from certain symptoms of type 2 diabetes. In comparison, diabetic rats fed with high-fat diet presented decreased but relatively stable blood glucose level, and this was significantly higher than that of the control group (P<0.05).

CONCLUSIONS

This model easily recovers with normal diet feeding. A high-fat diet is suggested as the background diet in future pharmacological studies using this model.

Agomelatine pretreatment prevents development of hyperglycemia and hypoinsulinemia in streptozotocin-induced diabetes in mice

The main objective of this study was to investigate potential effectiveness of agomelatine pretreatment in the prevention of diabetes itself and encephalopathy, with a focus on brain tissue oxidative stress and inflammatory processes in streptozotocin (STZ)-induced diabetic mice. Interleukine-1β (IL-1β) and TACR1 (NK1), which is a tachykinine receptor, were used for the investigation of inflammation in the brain regions including raphe nucleus, periaqueductal gyrus (PAG), amygdala, and nucleus accumbens. The effects of agomelatine on total antioxidant capacity were also evaluated. In the in vitro part of the study, the effects of agomelatine on cell viability were investigated in dorsal root ganglion (DRG) neurons. Fasting blood glucose levels were measured 72 h after STZ injection to determine the diabetic condition. Agomelatine pretreatment prevented both hyperglycemia and hypoinsulinemia in STZ-treated mice. When STZ was injected to induce diabetes in mice, neither hyperglycemia nor hypoinsulinemia was developed in agomelatine pretreated mice and 6 weeks after development of diabetes, agomelatine treatment significantly decreased levels of IL-1β mRNA in raphe nucleus and nucleus accumbens. TACR1 mRNA levels were lower in raphe nucleus, PAG, and amygdala of agomelatine-treated diabetic mice. The increase in total antioxidant capacity after agomelatine administration may responsible for its beneficial effect in the prevention of diabetes. We showed that agomelatine reversed high glucose-induced cell viability decreases in DRG neurons. Both the antihyperglycemic and antioxidant effects of agomelatine might have contributed to the DRG neuron viability improvement. In conclusion, agomelatine seems to both prevent development of diabetes and reverse the encephalopathic changes caused by diabetes.

Melatonin, mitochondria, and the metabolic syndrome

A number of risk factors for cardiovascular disease including hyperinsulinemia, glucose intolerance, dyslipidemia, obesity, and elevated blood pressure are collectively known as metabolic syndrome (MS). Since mitochondrial activity is modulated by the availability of energy in cells, the disruption of key regulators of metabolism in MS not only affects the activity of mitochondria but also their dynamics and turnover. Therefore, a link of MS with mitochondrial dysfunction has been suspected since long. As a chronobiotic/cytoprotective agent, melatonin has a special place in prevention and treatment of MS. Melatonin levels are reduced in diseases associated with insulin resistance like MS. Melatonin improves sleep efficiency and has antioxidant and anti-inflammatory properties, partly for its role as a metabolic regulator and mitochondrial protector. We discuss in the present review the several cytoprotective melatonin actions that attenuate inflammatory responses in MS. The clinical data that support the potential therapeutical value of melatonin in human MS are reviewed.

Effects of Melatonin on Glucose Homeostasis, Antioxidant Ability, and Adipokine Secretion in ICR Mice with NA/STZ-Induced Hyperglycemia

Diabetes is often associated with decreased melatonin level. The aim was to investigate the effects of different dosage of melatonin on glucose hemostasis, antioxidant ability and adipokines secretion in diabetic institute for cancer research (ICR) mice. Forty animals were randomly divided into five groups including control (C), diabetic (D), low-dosage (L), medium-dosage (M), and high-dosage (H) groups. Groups L, M, and H, respectively, received oral melatonin at 10, 20, and 50 mg/kg of BW (body weight) daily after inducing hyperglycemia by nicotinamide (NA)/ streptozotocin (STZ). After the six-week intervention, results showed that melatonin administration increased insulin level and performed lower area under the curve (AUC) in H group (p < 0.05). Melatonin could lower hepatic Malondialdehyde (MDA) level in all melatonin-treated groups and increase superoxide dismutase activity in H group (p < 0.05). Melatonin-treated groups revealed significant higher adiponectin in L group, and lower leptin/adiponectin ratio and leptin in M and H groups (p < 0.05). Melatonin could lower cholesterol and triglyceride in liver and decrease plasma cholesterol and low-density lipoprotein-cholesterol (LDL-C) in L group, and increase plasma high-density lipoprotein-cholesterol (HDL-C) in H group (p < 0.05). Above all, melatonin could decrease oxidative stress, increase the adiponectin level and improve dyslipidemia, especially in H group. These data support melatonin possibly being a helpful aid for treating hyperglycemia-related symptoms.

Protopanaxadiol and Protopanaxatriol-Type Saponins Ameliorate Glucose and Lipid Metabolism in Type 2 Diabetes Mellitus in High-Fat Diet/Streptozocin-Induced Mice

Ginsenoside is a major active component of ginseng, which exhibits various pharmacological properties such as hepatoprotection, tumor suppression and diabetes resistance. In this study, the anti-diabetic effects of protopanaxadiol (PPD) and protopanaxatriol (PPT)-type saponins were explored and compared in high-fat diet/streptozocin-induced type 2 diabetes mellitus (T2DM) mice. Our results showed that low or high dose (50 mg/kg bodyweight or 150 mg/kg bodyweight) PPD and PPT significantly reduced fasting blood glucose, improved glucose tolerance and insulin resistance in T2DM mice. PPD and PPT also regulated serum lipid-related markers such as reduced total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol in T2DM mice. In addition, PPD and PPT dramatically ameliorated the inflammatory responses by suppressing the secretion of pro-inflammatory cytokines like tumor necrosis factor-alpha and interleukin-6 in serum level and gene expression in liver level, and improved the antioxidant capacity by increasing the superoxide dismutase and decreasing malondialdehyde levels in the serum of T2DM mice. Moreover, the anti-diabetic effect of PPD and PPT appeared to be partially mediated by the suppression of hepatic metabolism genes expression such as peroxisome proliferator-activated receptor gamma coactivator 1-alpha, phosphoenolpyruvate carboxykinase, and glucose-6-phosphatase, as well as facilitating lipid metabolism genes expression such as microsomal TG transfer protein in the liver tissues of T2DM mice. Taken together, our results indicated that PPD and PPT might potentially act as natural anti-diabetic compounds to be used for preventing and treating the T2DM and its complications in the future.

Chronomedicine and type 2 diabetes: shining some light on melatonin

In mammals, the circadian timing system drives rhythms of physiology and behaviour, including the daily rhythms of feeding and activity. The timing system coordinates temporal variation in the biochemical landscape with changes in nutrient intake in order to optimise energy balance and maintain metabolic homeostasis. Circadian disruption (e.g. as a result of shift work or jet lag) can disturb this continuity and increase the risk of cardiometabolic disease. Obesity and metabolic disease can also disturb the timing and amplitude of the clock in multiple organ systems, further exacerbating disease progression. As our understanding of the synergy between the timing system and metabolism has grown, an interest has emerged in the development of novel clock-targeting pharmaceuticals or nutraceuticals for the treatment of metabolic dysfunction. Recently, the pineal hormone melatonin has received some attention as a potential chronotherapeutic drug for metabolic disease. Melatonin is well known for its sleep-promoting effects and putative activity as a chronobiotic drug, stimulating coordination of biochemical oscillations through targeting the internal timing system. Melatonin affects the insulin secretory activity of the pancreatic beta cell, hepatic glucose metabolism and insulin sensitivity. Individuals with type 2 diabetes mellitus have lower night-time serum melatonin levels and increased risk of comorbid sleep disturbances compared with healthy individuals. Further, reduced melatonin levels, and mutations and/or genetic polymorphisms of the melatonin receptors are associated with an increased risk of developing type 2 diabetes. Herein we review our understanding of molecular clock control of glucose homeostasis, detail the influence of circadian disruption on glucose metabolism in critical peripheral tissues, explore the contribution of melatonin signalling to the aetiology of type 2 diabetes, and discuss the pros and cons of melatonin chronopharmacotherapy in disease management.

The protective effect of the active components of ERPC on diabetic peripheral neuropathy in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Euonymus alatus, Radix trichosanthis, Panax notoginseng and Coptis chinensis are popular plants used in traditional Chinese medicine to treat diabetes.

AIM OF THE STUDY

The aim of the study is to investigate the therapeutic effect of the active components of Euonymus alatus, Radix trichosanthis, Panax notoginseng and Coptis chinensis (cERPC) on diabetic peripheral neuropathy in the rats and explore the underlying mechanism involved.

METHODS

After diabetes was induced in rats for 20 weeks, cERPC or water was administered for 12 weeks. After a hot plate test, motor nerve conduction velocity and sciatic nerve blood flow were determined; the sciatic nerves were isolated for toluidine blue staining; and the fibre area, fibre diameter, axon area, axon diameter and myelin thickness were evaluated. The levels of the myelin basic protein, myelin protein zero, Oct6 and Krox20 were measured by western blot or immunofluorescence.

RESULTS

cERPC was efficient in reducing the response latency, increasing motor nerve conduction velocity, enhancing sciatic nerve blood flow and ameliorating the pathological changes in diabetic rats. cERPC also had a role in increasing the levels of myelin basic protein and myelin protein zero and improving the expression of Oct6 and Krox20 in sciatic nerves of diabetic rats.

CONCLUSIONS

cERPC ameliorates diabetic peripheral neuropathy by attenuating electrophysiological, circulatory and morphological alterations, which is mediated by the Oct6-Krox20 pathway.

Metabolic effects of quail eggs in diabetes-induced rats: comparison with chicken eggs

BACKGROUND

Quail eggs as a food item have recently been introduced into the diet of some Cameroonians. These eggs are being sold in local markets, but with many unfounded health claims. One claim is that quail eggs can reduce blood glucose levels in diabetics. It was therefore necessary to evaluate the effect of consuming quail eggs on blood glucose levels, lipid profiles, and oxidative stress parameters in diabetes-induced rats.

METHODS

Twenty Wistar rats weighing, on average, 250 g were divided into four groups of five rats each. Group 1 consisted of rats with normal blood glucose, and the other three groups (2, 3, and 4) consisted of diabetes-induced rats achieved by intravenous injection of streptozotocin. During 16 days, rats in groups 1 and 2 received distilled water; and rats in groups 3 and 4 received quail and chicken eggs, respectively, with gastroesophageal probe at a dose of 1 mL/200 g body weight. Fasting blood glucose levels were determined in all the groups on the 1st, 7th, 14th, and 17th days after induction of diabetes. On the 17th day, the fasting rats were sacrificed, and blood and liver samples were collected for biochemical analyses.

RESULTS

In 17 days, the consumption of quail and chicken eggs had no effect on blood glucose levels of diabetic rats. Total cholesterol levels were higher in groups 3 (75.59 mg/dL) and 4 (59.41 mg/dL) compared to group 2 (55.67 mg/dl), although these differences were not significant (all p>0.05). Triglyceride levels were significantly higher (p<0.05) in groups 3 (106.52 mg/dL) and 4 (109.65 mg/dL) compared to group 2 (65.82 mg/dL). Quail eggs had no effect on oxidative stress parameters (malondialdehyde, hydroperoxides, and catalase).

CONCLUSIONS

The consumption of quail eggs by diabetic rats at the tested dose had no effect on blood glucose level and oxidative stress parameters and may have a negative effect on lipid profile.

Beneficial Effect of Leptin on Spatial Learning and Memory in Streptozotocin-Induced Diabetic Rats

BACKGROUND

Diabetes mellitus is a chronic disease which may be accompanied by cognitive impairments. The expression of the obesity gene (ob) is decreased in insulin-deficient diabetic animals and increased after the administration of insulin or leptin. Plasma leptin levels are reduced in the streptozotocin (STZ)-induced diabetic rats. Therefore, the deleterious effects of diabetes on memory may be due to the reduction of leptin.

AIMS

Investigate the effect of subcutaneous injection of leptin on spatial learning and memory in STZ-induced diabetic rats.

STUDY DESIGN

Animal experimentation.

METHODS

The rats were divided into three groups: 1-control, 2- diabetic, and 3- diabetic-leptin. Diabetes was induced in groups 2 and 3 by STZ injection (55 mg/kg) intraperitoneally (i.p). The animals received leptin (0.1 mg/kg) or saline subcutaneously (s.c) for 10 days before behavioral studies. Then, they were examined in the Morris water maze over 3 blocks after 3 days of the last injection of leptin.

RESULTS

The travelled path length and time spent to reach the platform significantly increased in the diabetic group (p<0.001) and decreased with leptin treatment (p<0.01 & p<0.001 respectively); also, a significant increase in path length and time was observed between the diabetic-leptin group and the diabetic group (p<0.01, p<0.001, respectively) in the probe test.

CONCLUSION

Leptin can exert positive effects on memory impairments in diabetic rats.

The Effect of Melatonin on Bone Loss, Diabetic Control, and Apoptosis in Rats With Diabetes With Ligature-Induced Periodontitis

BACKGROUND

The aim of this study examines the effect of systemic melatonin administration on proinflammatory cytokine levels, apoptosis, alveolar bone loss (ABL), lipid metabolism, and diabetic control in in rats with diabetes mellitus (DM) and ligature-induced periodontitis.

METHODS

Fifty-two male Wistar rats were used in this study. Study groups were as follows: 1) non-ligated control (NL, n = 6); 2) streptozotocin (STZ, n = 8); 3) STZ and melatonin (STZ+Mel, n = 8); 4) ligature (L, n = 6); 5) ligature and melatonin (L+Mel, n = 8); 6) STZ and ligature (STZ+L, n = 8); and 7) STZ, ligature, and melatonin (STZ+L+Mel, n = 8). DM was induced by intraperitoneal injection of a single dose of STZ (60 mg/kg). Melatonin was administered by intraperitoneal injection of a dose of 10 mg/kg/day for 4 weeks. Silk ligatures were placed subgingivally around the mandibular right first molars. The study period was 4 weeks, and animals were sacrificed at the end of 4 weeks. Morphometric analysis of bone loss was performed. Tissues were histopathologically examined. Inducible nitric oxide synthase (iNOS) and B-cell lymphoma-2-associated X (bax) protein expressions, serum interleukin (IL)-1β levels, and tartrate-resistant acid phosphatase-positive (TRAP+) osteoclast numbers were also evaluated.

RESULTS

After 4 weeks, the highest ABL was observed in the STZ+L group, and the difference was significant (P <0.05). Systemically administered melatonin significantly decreased ABL in the STZ+L+Mel group compared with that in the STZ+L group (P <0.05). TRAP+ osteoclast numbers were the highest in the STZ+L group, and melatonin significantly decreased osteoclast numbers (P <0.05) but had no effect on iNOS, IL-1β, or bax levels.

CONCLUSIONS

Within the limits of this study, it can be concluded that systemic melatonin treatment may decrease osteoclastic activity and reduce ABL in the model using rats with DM.

Effect of exogenous leptin on serum levels of lipids, glucose, renal and hepatic variables in both genders of obese and streptozotocin-induced diabetic rats

OBJECTIVES

Leptin exerts various effects on appetite and body weight. Disruption of the obesity gene is precedent to fatness. Insulin or glucose elevates leptin, but streptozotocin reduces it. However, controversial data exist for the effects of leptin on diabetes and leptin level in each gender. Leptin can damage the kidney function but little evidence exists for its hepatic effects. The aim of this study was to investigate the probable sex-dependent differences in blood sugar levels, lipid profile, and renal and hepatic biochemical factors in the obesity and streptozotocin-induced diabetic rats after leptin administration.

MATERIALS AND METHODS

Wistar rats of both sexes were randomly divided into two groups, namely obese and diabetic rats. Each group was further divided into male and female subgroups. Extra fat and carbohydrate was added to the diet to induce obesity. Furthermore, streptozotocin (55 mg/kg, IP) was injected to induce diabetes. The treatment groups received leptin (0.1 mg/kg SC) for 10 days, and then, blood samples were taken from the orbital sinus for laboratory evaluations.

RESULTS

Leptin resulted in a significant weight loss in both sexes (P<0.001), food intake reduction in male rats (P<0.05), LDL reduction in female rats (obese (P<0.05) and diabetic (P<0.001)), and glucose level decline in the female diabetic rats (P<0.001). However, total protein concentration, LFT (liver function tests), urea and creatinin concentrations among different groups did not show any significant changes.

CONCLUSION

Leptin caused some discrepant results, especially regarding the LDL and glucose levels in diabetic female rats.

Effect of Stay-Green Wheat, a Novel Variety of Wheat in China, on Glucose and Lipid Metabolism in High-Fat Diet Induced Type 2 Diabetic Rats

The use of natural hypoglycemic compounds is important in preventing and managing Type 2 diabetes mellitus (T2DM). Forty male Sprague-Dawley rats weighing 150–180 g were divided into four groups to investigate the effects of the compounds in stay-green wheat (SGW), a novel variety of wheat in China, on T2DM rats. The control group (NDC) was fed with a standard diet, while T2DM was induced in the rats belonging to the other three groups by a high-fat diet followed by a streptozotocin (STZ) injection. The T2DM rats were further divided into a T2DM control group (DC), which was fed with the normal diet containing 50% common wheat flour, a high dose SGW group (HGW) fed with a diet containing 50% SGW flour, and a low dose SGW group (LGW) fed with a diet containing 25% SGW flour and 25% common wheat flour. Our results showed that SGW contained cereal antioxidants, particularly high in flavonoids and anthocyanins (46.14 ± 1.80 mg GAE/100 g DW and 1.73 ± 0.14 mg CGE/100 g DW, respectively). Furthermore, SGW exhibited a strong antioxidant activity in vitro (30.33 ± 2.66 μg TE/g DW, p < 0.01). Administration of the SGW at a high and low dose showed significant down-regulatory effects on fasting blood glucose (decreasing by 11.3% and 7.0%, respectively), insulin levels (decreasing by 12.3% and 9.7%, respectively), and lipid status (decreasing by 9.1% and 7.5%, respectively) in T2DM rats (p < 0.01). In addition, the T2DM groups treated with SGW at a high and low dose showed a significant increase in the blood superoxide dismutase (1.17 fold and 1.15 fold, respectively) and glutathione peroxidase activities (1.37 fold and 1.30 fold, respectively) compared with the DC group (p < 0.01). The normalized impaired antioxidant status of the pancreatic islet and of the liver compared with the DC group was also significantly increased. Our results indicated that SGW components exerting a glycemic control and a serum lipid regulation effect may be due to their free radical scavenging capacities to reduce the risk of T2DM in experimental diabetic rats.