Accumulating evidence suggests the existence of a strong link between metabolic syndrome and neurodegeneration. Indeed, epidemiologic studies have described solid associations between metabolic syndrome and neurodegeneration, whereas animal models contributed for the clarification of the mechanistic underlying the complex relationships between these conditions, having the development of an insulin resistance state a pivotal role in this relationship. Herein, we review in a concise manner the association between metabolic syndrome and neurodegeneration. We start by providing concepts regarding the role of insulin and insulin signaling pathways as well as the pathophysiological mechanisms that are in the genesis of metabolic diseases. Then, we focus on the role of insulin in the brain, with special attention to its function in the regulation of brain glucose metabolism, feeding, and cognition. Moreover, we extensively report on the association between neurodegeneration and metabolic diseases, with a particular emphasis on the evidence observed in animal models of dysmetabolism induced by hypercaloric diets. We also debate on strategies to prevent and/or delay neurodegeneration through the normalization of whole-body glucose homeostasis, particularly via the modulation of the carotid bodies, organs known to be key in connecting the periphery with the brain.

Dopamine directly acts in the liver and white adipose tissue (WAT) to regulate insulin signaling, glucose uptake, and catabolic activity. Given that dopamine is secreted by the gut and regulates insulin secretion in the pancreas, we aimed to determine its regulation by nutritional cues and its role in regulating glucagon-like peptide 1 (GLP-1) action in WAT. Solutions with different nutrients were administered to Wistar rats and postprandial dopamine levels showed elevations following a mixed meal and glucose intake. In high-fat diet-fed diabetic Goto-Kakizaki rats, sleeve gastrectomy upregulated dopaminergic machinery, showing the role of the gut in dopamine signaling in WAT. Bromocriptine treatment in the same model increased GLP-1R in WAT, showing the role of dopamine in regulating GLP-1R. By contrast, treatment with the GLP-1 receptor agonist Liraglutide had no impact on dopamine receptors. GLP-1 and dopamine crosstalk was shown in rat WAT explants, since dopamine upregulated GLP-1-induced AMPK activity in mesenteric WAT in the presence of the D2R and D3R inhibitor Domperidone. In human WAT, dopamine receptor 1 (D1DR) and GLP-1R expression were correlated. Our results point out a dietary and gut regulation of plasma dopamine, acting in the WAT to regulate GLP-1 action. Together with the known dopamine action in the pancreas, such results may identify new therapeutic opportunities to improve metabolic control in metabolic disorders.

Maternal obesity and gestational diabetes predispose the next generation to metabolic disturbances. Moreover, the lactation phase also stands as a critical phase for metabolic programming. Nevertheless, the precise mechanisms originating these changes remain unclear. Here, we investigate the consequences of a maternal lipid-rich diet during gestation and lactation and its impact on metabolism and behavior in the offspring. Two experimental groups of Wistar female rats were used: a control group (NC) that was fed a standard diet during the gestation and lactation periods and an overnutrition group that was fed a high-fat diet (HF, 60% lipid-rich) during the same phases. The offspring were analyzed at postnatal days 21 and 28 and at 2 months old (PD21, PD28, and PD60) for their metabolic profiles (weight, fasting glycemia insulin sensitivity, and glucose tolerance) and euthanized for brain collection to evaluate metabolism and inflammation in the hypothalamus, hippocampus, and prefrontal cortex using Western blot markers of synaptic dynamics. At 2 months old, behavioral tests for anxiety, stress, cognition, and food habits were conducted. We observed that the female offspring born from HF mothers exhibited increased weight gain and decreased glucose tolerance that attenuated with age. In the offspring males, weight gain increased at P21 and worsened with age, while glucose tolerance remained unchanged. The offspring of the HF mothers exhibited elevated levels of anxiety and stress during behavioral tests, displaying decreased predisposition for curiosity compared to the NC group. In addition, the offspring from mothers with HF showed increased food consumption and a lower tendency towards food-related aggression. We conclude that exposure to an HF diet during pregnancy and lactation induces dysmetabolism in the offspring and is accompanied by heightened stress and anxiety. There was sexual dimorphism in the metabolic traits but not behavioral phenotypes.

Food behaviour is a complex and multifaceted cooperation between physiologic, psychological, social, and genetic factors, influencing meal timing, amount of food intake, food preferences, and food selections. Deregulation of the neurobiological mechanisms controlling food behaviour underlies the development of obesity and type 2 diabetes, two epidemics of the present century. Several brain nuclei are involved in the regulation of the different components of food behaviours; the hypothalamus is the key in controlling appetite and energy homeostasis. In this review, we will explain the role of the hypothalamus in the control of food intake and its interplay with other brain nuclei important in food behaviour. We will also highlight the deregulation of satiety pathways in type 2 diabetes and obesity and the mechanisms behind this deregulation. Finally, knowing that there are different categories of sugars and that they differently impact food behaviours, we will review in a concise manner the studies referring to the effects of sugars in satiety and reward pathways and their impacts on metabolic diseases.

Maternal obesity and gestational diabetes predispose to metabolic disturbances in the next generation. Moreover, the lactation phase also stands as critical for metabolic programming. Nevertheless, the precise mechanisms originating these changes remain unclear. Here we investigate the consequences of maternal diet lipid-rich diet during gestation and lactation, and its impact on metabolism and behavior in the offspring. Two experimental groups of Wistar female rats were used: a control group (NC) that fed a standard diet during gestation and lactation periods and an overnutrition group that fed a high-fat diet (HF, 60% lipid-rich) during the same phases. Offspring were analyzed at postnatal days 21, 28, and 2 months-old (PD21, PD28, PD60) for metabolic profile (weight, fasting glycemia insulin sensitivity, glucose tolerance) and euthanized for brain collection to evaluate by western blot markers of synaptic dynamics, metabolism and inflammation in the hypothalamus, hippocampus and prefrontal cortex. At 2 months-old, behavioral tests for anxiety, stress, cognition, and food habits were conducted. We observe that female offspring born from HF mothers exhibited increased weight gain and decreased glucose tolerance that attenuates with age. In offspring males, weight gain increased at P21 and worsened with age, while glucose tolerance remained unchanged. Offspring of HF mothers exhibited elevated levels of anxiety and stress during behavioral tests, displaying decreased predisposition for curiosity compared to the NC group. In addition, offspring from mothers with HF showed increased food consumption and a lower tendency towards food-related aggression. We conclude that exposure to HF diet during pregnancy and lactation induces dysmetabolism in the offspring accompanied by heightened stress and anxiety. There was sexual dimorphism in metabolic traits but not behavioral phenotypes.