Cardiac autonomic neuropathy (CAN) is one of the earliest complications of type 2 diabetes (T2D), presenting a silent cause of cardiovascular morbidity and mortality. Recent research relates the pathogenesis of cardiovascular disease in T2D to an ensuing chronic, low-grade proinflammatory and pro-oxidative environment, being the hallmark of the metabolic syndrome. Metabolic inflammation emerges as adipose tissue inflammatory changes extending systemically, on the advent of hyperglycemia, to reach central regions of the brain. In light of changes in glucose and insulin homeostasis, dysbiosis or alteration of the gut microbiome (GM) emerges, further contributing to inflammatory processes through increased gut and blood–brain barrier permeability. Interestingly, studies reveal that the determinants of oxidative stress and inflammation progression exist at the crossroad of CAN manifestations, dictating their evolution along the natural course of T2D development. Indeed, sympathetic and parasympathetic deterioration was shown to correlate with markers of adipose, vascular, and systemic inflammation. Additionally, evidence points out that dysbiosis could promote a sympatho-excitatory state through differentially affecting the secretion of hormones and neuromodulators, such as norepinephrine, serotonin, and γ-aminobutyric acid, and acting along the renin–angiotensin–aldosterone axis. Emerging neuronal inflammation and concomitant autophagic defects in brainstem nuclei were described as possible underlying mechanisms of CAN in experimental models of metabolic syndrome and T2D. Drugs with anti-inflammatory characteristics provide potential avenues for targeting pathways involved in CAN initiation and progression. The aim of this review is to delineate the etiology of CAN in the context of a metabolic disorder characterized by elevated oxidative and inflammatory load.

Background: The complexity of the interaction between metabolic dysfunction and cardiovascular complications has long been recognized to extend beyond simple perturbations of blood glucose levels. Yet, structured interventions targeting the root pathologies are not forthcoming. Growing evidence implicates the inflammatory changes occurring in perivascular adipose tissue (PVAT) as early instigators of cardiovascular deterioration. Methods and Results: We used a nonobese prediabetic rat model with localized PVAT inflammation induced by hypercaloric diet feeding, which dilutes inorganic phosphorus (Pi) to energy ratio by 50%, to investigate whether Pi supplementation ameliorates the early metabolic impairment. A 12‐week Pi supplementation at concentrations equivalent to and twice as much as that in the control diet was performed. The localized PVAT inflammation was reversed in a dose‐dependent manner. The increased expression of UCP1 (uncoupling protein1), HIF‐1α (hypoxia inducible factor‐1α), and IL‐1β (interleukin‐1β), representing the hallmark of PVAT inflammation in this rat model, were reversed, with normalization of PVAT macrophage polarization. Pi supplementation restored the metabolic efficiency consistent with its putative role as an UCP1 inhibitor. Alongside, parasympathetic autonomic and cerebrovascular dysfunction function observed in the prediabetic model was reversed, together with the mitigation of multiple molecular and histological cardiovascular damage markers. Significantly, a Pi‐deficient control diet neither induced PVAT inflammation nor cardiovascular dysfunction, whereas Pi reinstatement in the diet after a 10‐week exposure to a hypercaloric low‐Pi diet ameliorated the dysfunction. Conclusions: Our present results propose Pi supplementation as a simple intervention to reverse PVAT inflammation and its early cardiovascular consequences, possibly through the interference with hypercaloric‐induced increase in UCP1 expression/activity.

β₃-Adrenoceptors mediate several functions in rodents that could be beneficial for the treatment of obesity and type 2 diabetes. This includes promotion of insulin release from the pancreas, cellular glucose uptake, lipolysis, and thermogenesis in brown adipose tissue. In combination, they lead to a reduction of body weight in several rodent models including ob/ob mice and Zucker diabetic fatty rats. These findings stimulated drug development programs in various pharmaceutical companies, and at least nine β₃-adrenoceptor agonists have been tested in clinical trials. However, all of these projects were discontinued due to the lack of clinically relevant changes in body weight. Following a concise historical account of discoveries leading to such drug development programs we discuss species differences that explain why β₃-adrenoceptors are not a meaningful drug target for the treatment of obesity and type 2 diabetes in humans.

Metabolic disease complications pose a significant health risk due to their early development, making their diagnosis and radical therapy a considerable challenge. Here, we present a protocol for producing a rat model of non-obese prediabetes characterized by hyperinsulinemia, normoglycemia, and normal body weight. We describe steps for inducing the model in Sprague-Dawley (SD) male and ovariectomized female rats by free feeding on a mild hypercaloric diet. This protocol offers a potential model of metabolically unhealthy lean individuals. For complete details on the use and execution of this protocol, please refer to Elkhatib et al.¹ and Dwaib et al.².

β3-Adrenoceptors mediate several functions in rodents that could be beneficial for the treatment of obesity and type 2 diabetes. This includes promotion of insulin release from the pancreas, of cellular glucose uptake, of lipolysis, and of thermogenesis in brown adipose tissue. In combination, they lead to a reduction of body weight in several rodent models including ob/ob mice and Zucker diabetic fatty rats. These findings stimulated drug development programs in various pharmaceutical companies, and at least nine β3-adrenoceptor agonists have been tested in clinical trials. However, all of these projects were discontinued due to lack of clinically relevant changes of body weight. Following a concise historical account of discoveries leading to such drug development programs we discuss species differences that explain why β3-adrenoceptors are not a meaningful drug target for the treatment of obesity and type 2 diabetes in humans.

ID 15333 Poster Board 358 Prediabetes is a transitional stage in the progression of Type 2 Diabetes where diabetes-related cardiovascular (CV) complications begin. Our previous work on non-obese prediabetic male rats showed that early CV and metabolic impairments were associated with confined dysfunction in the thoracic perivascular adipose tissue (PVAT) characterized by inflammation and hypoxia. There has been neither recommendations for pharmacological treatment to interrupt the hypoxic machinery in PVAT, nor clear sexual dimorphism in PVAT involvement at this stage, we therefore hypothesized that therapeutic fasting (TF) can alleviate PVAT dysfunction, metabolic and CV stress among Mild hyper-caloric (MHC)-fed rats in a sex dependent manner. Sprague-Dawley rats from both sexes (4-5weeks) were allocated into 3 groups: control diet (C), MHC diet and MHC-diet with TF, for 24 weeks. Rats were fed ad libitum in the first 12 weeks. Afterwards, the TF group were subjected to daily fasting from 7.00pm -7.00am for 12 weeks with free access to water, and to MHC-diet otherwise. Daily food intake, body weight, blood glucose, body composition (using NMR), HbA1c, serum insulin levels, echocardiographic parameters, and noninvasive blood pressure were measured. At week 24; rats were catheterized for invasive hemodynamic examination. Cardiac autonomic neuropathy was assessed by measuring baroreceptor sensitivity using the vasoactive method. After sacrifice, aortic contractility and endothelial function were measured using organ bath experiments and molecular investigation was performed on various adipose pools, in addition to cardiac and aortic tissues. To assess the role of female sex hormones 3 additional groups of females were bilaterally ovariectomized (OVX) on week 12, then the same feeding groups (C, MHC and MH-TF) were applied for the remaining 12 weeks. The same set of parameters and experiments were measured and conducted. As expected, MHC feeding induced non-obese prediabetes, signs of early cardiovascular and metabolic dysfunction with and PVAT impairment in male rats. Intact female rats resisted MHC-induced derangements, while OVX females presented an obese prediabetic phenotype, with CV and metabolic impairments and PVAT dysfunction. Moreover, on the molecular and histochemical levels, cardiac and aortic tissues as well as brainstem presented pathologies in the MHC arms presented by increased macrophage infiltration and oxidative stress in all tissues, plus an increased fibrosis in the cardiac and aortic ones. Strikingly, TF in the presence of MHC feeding and in the absence of calorie restriction, and estrogen in the case of females, seemed to substantially correct these alterations in both male and OVX rats and interrupt hypoxia in PVAT. Taken together, our work suggests a novel understanding whereby TF interferes with the hypoxia machinery in PVAT and mitigates prediabetes and related CV insults in a sex dependent manner.