Low-frequency electroacupuncture improves disordered hepatic energy metabolism in insulin-resistant Zucker diabetic fatty rats via the AMPK/mTORC1/p70S6K signaling pathway

Background and aim: Disordered hepatic energy metabolism is found in obese rats with insulin resistance (IR). There are insufficient experimental studies of electroacupuncture (EA) for IR and type 2 diabetes mellitus (T2DM). The aim of this study was to probe the effect of EA on disordered hepatic energy metabolism and the adenosine monophosphate (AMP)-activated protein kinase (AMPK)/mammalian target of rapamycin complex 1 (mTORC1)/ribosomal protein S6 kinase, 70-kDa (p70S6K) signaling pathway. Methods: Zucker Diabetic Fatty (ZDF) rats were randomly divided into three groups: EA group receiving EA treatment; Pi group receiving pioglitazone gavage; and ZF group remaining untreated (n = 8 per group). Inbred non-insulin-resistant Zucker lean rats formed an (untreated) healthy control group (ZL, n = 8). Fasting plasma glucose (FPG), fasting insulin (FINS), C-peptide, C-reactive protein (CRP) and homeostatic model assessment of insulin resistance (HOMA-IR) indices were measured. Hematoxylin–eosin (H&E) staining was used to investigate the liver morphologically. The mitochondrial structure of hepatocytes was observed by transmission electron microscopy (TEM). Western blotting was adopted to determine protein expression of insulin receptor substrate 1 (IRS-1), mTOR, mTORC1, AMPK, tuberous sclerosis 2 (TSC2) and p70S6K, and their phosphorylation. RT-PCR was used to quantify IRS-1, mTOR, mTORC1, AMPK and p70S6K mRNA levels. Results: Compared with the ZF group, FPG, FINS, C-peptide, CRP and HOMA-IR levels were significantly reduced in the EA group ( p < 0.05, p < 0.01). Evaluation of histopathology showed improvement in liver appearances following EA. Phosphorylation levels of AMPK, mTOR and TSC2 decreased, and IRS-1 and p70S6K increased, in hepatocytes of the ZF group, while these negative effects appeared to be alleviated by EA. Conclusions: EA can effectively ameliorate IR and regulate energy metabolism in the ZDF rat model. AMPK/mTORC1/p70S6K and related molecules may represent a potential mechanism of action underlying these effects.

Estrogen Impairs Adipose Tissue Expansion and Cardiometabolic Profile in Obese-Diabetic Female Rats

It has been reported that 17β-estradiol (E2) can exert beneficial effects against the development of obesity, providing women with a healthier metabolic profile and conferring cardiovascular protection. However, a growing body of evidence questions this role in the context of obesity and diabetes. We focus on the adipose tissue–heart axis to address the question of whether E2 can have metabolically detrimental effects in an obese-diabetic rat model. Female Zucker Diabetic Fatty rats were used: LEAN, fa/+; SHAM, sham-operated fa/fa; OVA, ovariectomized fa/fa, and OVA+E2, ovariectomized and E2 treated fa/fa. The secretory expression profile, tissue expansion parameters and composition of visceral adipose tissue, as well as systemic and cardiac parameters related to insulin resistance, fibrosis, and inflammation were analyzed. Ovariectomy induced an attenuation of both diabetic condition and metabolic dysfunction of adipose tissue and cardiac muscle in fa/fa rats, suggesting that E2, in the context of diabetes and obesity, loses its cardioprotective role and could even contribute to greater metabolic alterations. Adipose tissue from OVA rats showed a healthier hyperplastic expansion pattern, which could help maintain tissue function, increase adiponectin expression, and decrease pro-inflammatory adipokines. These findings should be taken into account when considering hormone replacement therapy for obese-diabetic women.

The Effects of Erchen Decoction on Gut Microbiota and Lipid Metabolism Disorders in Zucker Diabetic Fatty Rats

Obesity is a chronic metabolic disease caused by genetic and environmental factors that has become a serious global health problem. There is evidence that gut microbiota is closely related to the occurrence and development of obesity. Erchen Decoction (ECD), a traditional Chinese medicine, has been widely used for clinical treatment and basic research of obesity and related metabolic diseases in recent years. It can significantly improve insulin resistance (IR) and lipid metabolism disorders. However, there is no microbiological study on its metabolic regulation. In this study, we investigated the effects of ECD on obesity, especially lipid metabolism and the composition and function of gut microbiota in Zucker diabetic fatty (ZDF) rats, and explored the correlation between the biomarkers of gut microbiota and metabolite and host phenotype. The results showed that ECD could reduce body weight, improve IR and lipid metabolism, and reduce the concentration of free fatty acids (FFA) released from white adipose tissue (WAT) due to excessive lipolysis by interfering with the insulin receptor substrate 1 (IRS1)/protein kinase B (AKT)/protein kinase A (PKA)/hormone-sensitive triglyceride lipase (HSL) signaling pathway in ZDF rats. Additionally, ECD gradually adjusted the overall structure of changed gut microbiota, reversed the relative abundance of six genera, and changed the function of gut microbiota by reducing the content of propionic acid, a metabolite of gut microbiota, in ZDF rats. A potentially close relationship between biomarkers, especially Prevotella, Blautia, and Holdemania, propionic acid and host phenotypes were demonstrated through correlation analysis. The results suggested that the beneficial effects of ECD on obesity, especially lipid metabolism disorders, are related to the regulation of gut microbiota in ZDF rats. This provides a basis for further research on the mechanism and clinical application of ECD to improve obesity via gut microbiota.

Effects of bee bread, Cornelian cherries treatment on the femoral bone structure using Zucker diabetic fatty rats as an animal model

: This is a pilot study dealing with the reduced femoral bone structure in Zucker diabetic fatty (ZDF) rats following a 10 week treatment with bee bread and Cornelian cherries. The adult ZDF rats were divided into 4 groups: the E1 group received bee bread (500 mg/kg b.w. daily), the E2 group received Cornelian cherries (500 mg/kg b.w. per day), the E3 group was simultaneously supplemented by bee bread and Cornelian cherries (500 + 500 mg/kg b.w. daily), and the C group served as an untreated diabetic control. A non-significant decrease in the blood glucose, total cholesterol, triglyceride concentrations, ALP activity and a non-significant increase in the insulin, total body weight of the ZDF rats, femoral length and weight were observed in the E1, E2, and E3 groups. The treatments had no impact on the relative volume of the cortical bone, bone mineral density, bone surface and cortical bone thickness. On the contrary, the relative volume of the trabecular bone, trabecular thickness and trabecular bone surface were significantly increased in the E1 group. The relative volume of the trabecular bone and trabecular thickness were significantly elevated in the E2 group. In the E3 group, the trabecular thickness was found to have significantly increased. Single administrations of either bee bread or Cornelian cherries had more positive effects on the trabecular bone microarchitecture in the ZDF rats than the simultaneous supplementation.

Vitamin A Status Regulates the Development of Obesity and Type 2 Diabetes in Zucker Diabetic Fatty Rats

Objectives Here, we studied the effects of VA status on the development of obesity and type 2 diabetes in Zucker diabetic fat (ZDF) rats. Methods Zucker Lean (ZL) and ZDF rats at weaning were divided into 6 groups, VA deficient with basal fat (VAD-BF, 0 mg retinyl palmitate (RP)/kg and 22.1% fat energy), VA marginal with BF (VAM-BF, 0.35 mg RP/kg), VA sufficient with BF (VAS-BF, 4.0 mg RP/kg), VAD with high-fat (VAD-HF, 60% fat energy), VAM-HF and VAS-HF diets, and fed for 8 weeks (w). The body mass (BM), and peripheral blood glucose (PBG) were measured weekly. An oral glucose tolerance test (OGTT) were done at 6.5 and 7.5w, respectively. Plasma levels of glucose, insulin, triacylglycerol and cholesterol l were determined using commercially available kits. The expression levels of genes and proteins in the liver of rats were analyzed using PCR and Western blot. Results VAS-BF ZL and ZDF rats from 6w had respectively higher BM than VAD/VAM-BF ZL and ZDF rats. VAS-HF ZL and ZDF rats from 4w had respectively higher BM than VAD/VAM-HF ZL and ZDF rats. VAS-BF/HF ZDF rats from 6w had respectively higher PBG levels than VAD/VAM-BF/HF ZDF rats. The OGTT AUC values of VAS-BF/HF ZL/ZDF rats were respectively higher than that of VAD/VAM-BF/HF ZL/ZDF rats. The levels of glucose, insulin, triacylglycerol and cholesterol in VAD/VAM/VAS-BF ZDF and VAD/VAM/VAS-HF ZDF rats were higher than that in BF ZL rats (except for the glucose level) and HF ZL rats, respectively. The hepatic Gck mRNA and its protein levels in VAD-BF ZL rats were lower than that in VAS-BF ZL rats. The hepatic levels of Fas, and Acl mRNA and FAS, and ACL proteins in VAM/VAS-HF ZF rats were higher than that in VAM/VAS-HF ZL rats. The hepatic retinol content of VAD-BF/HF ZL/ZDF rats were lower than that of VAM groups, which are lower than that of VAS-BF/HF ZL/ZDF rats. Conclusions VA statuses affect BM gain in ZL and ZDF rats fed a BF or a HF diet. The expression levels of mRNAs and proteins in the fatty acid biosynthesis pathways were reduced in VAD-HF ZDF rats. The effects of VA on fatty acid biosynthesis in ZDF rats were masked in a HF diet setting. Reduced VA intake prevents obesity, and type 2 diabetes in ZDF rats. Funding Sources Diabetes Action Research and Education Foundation

Matrix Metalloproteinases and Their Role in Mechanisms Underlying Effects of Quercetin on Heart Function in Aged Zucker Diabetic Fatty Rats

Several mechanisms may contribute to cardiovascular pathology associated with diabetes, including dysregulation of matrix metalloproteinases (MMPs). Quercetin (QCT) is a substance with preventive effects in treatment of cardiovascular diseases and diabetes. The aim of the present study was to explore effects of chronic QCT administration on changes in heart function in aged lean and obese Zucker Diabetic Fatty (ZDF) rats and that in association with MMPs. Signaling underlying effects of diabetes and QCT were also investigated. In the study, we used one-year-old lean and obese ZDF rats treated for 6 weeks with QCT. Results showed that obesity worsened heart function and this was associated with MMP-2 upregulation, MMP-28 downregulation, and inhibition of superoxide dismutases (SODs). Treatment with QCT did not modulate diabetes-induced changes in heart function and MMPs. However, QCT activated Akt kinase and reversed effects of diabetes on SODs inhibition. In conclusion, worsened heart function due to obesity involved changes in MMP-2 and MMP-28 and attenuation of antioxidant defense by SOD. QCT did not have positive effects on improvement of heart function or modulation of MMPs. Nevertheless, its application mediated activation of adaptive responses against oxidative stress through Akt kinase and prevention of diabetes-induced negative effects on antioxidant defense by SODs.

Identification of Novel Biomarker for Early Detection of Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most common complications of diabetes mellitus. After development of DN, patients will progress to end-stage renal disease, which is associated with high morbidity and mortality. Here, we developed early-stage diagnostic biomarkers to detect DN as a strategy for DN intervention. For the DN model, Zucker diabetic fatty rats were used for DN phenotyping. The results revealed that DN rats showed significantly increased blood glucose, blood urea nitrogen (BUN), and serum creatinine levels, accompanied by severe kidney injury, fibrosis and microstructural changes. In addition, DN rats showed significantly increased urinary excretion of kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL). Transcriptome analysis revealed that new DN biomarkers, such as complementary component 4b (C4b), complementary factor D (CFD), C-X-C motif chemokine receptor 6 (CXCR6), and leukemia inhibitory factor (LIF) were identified. Furthermore, they were found in the urine of patients with DN. Since these biomarkers were detected in the urine and kidney of DN rats and urine of diabetic patients, the selected markers could be used as early diagnosis biomarkers for chronic diabetic nephropathy.

Transcutaneous auricular vagal nerve stimulation inhibits hypothalamic P2Y1R expression and attenuates weight gain without decreasing food intake in Zucker diabetic fatty rats

Zucker diabetic fatty (ZDF) rats that harbor a mutation in the leptin receptor innately develop type 2 diabetes (T2D) with obesity. Transcutaneous auricular vagal nerve stimulation (taVNS) has an antidiabetic effect in ZDF rats. However, the underlying mechanisms of the weight-gain attenuating effect in ZDF rats by taVNS is still unclear. This study aimed to assess whether the weight-gain attenuating effect of taVNS in ZDF rats is associated with changes in the central nervous system (CNS) expression of P2Y1 receptors (P2Y1R). Adult male ZDF rats were subjected to taVNS and transcutaneous non-vagal nerve stimulation (tnVNS). Their food intake and body weight were recorded daily and weekly, respectively. P2Y1R expression in the hypothalamus, amygdala, and hippocampus was evaluated by western blotting. Hypothalamic P2Y1R expressing cells were detected using immunohistochemistry. Naïve ZDF rats were much heavier ( p < 0.05) than their lean littermates (ZL rats), with elevated hypothalamic P2Y1R expression ( p < 0.05). Further, taVNS but not tnVNS attenuated weight gain ( p < 0.05) without decreasing food intake ( p > 0.05) and suppressed hypothalamic P2Y1R expression in ZDF rats ( p < 0.05). Moreover, P2Y1R showed major expression in astrocytes of ZDF rats’ hypothalamus. ZDF rats innately develop obesity associated with elevated hypothalamic P2Y1R expression. taVNS attenuates weight gain in ZDF rats without changes in food intake, suggesting increased energy expenditure. Whether the reduced hypothalamic P2Y1R expression in response to taVNS is mechanistically linked to the increased energy expenditure remains to be determined.