This study aimed to investigate the pathophysiology of hepatic microcirculatory dysfunction in non-alcoholic fatty liver disease (NAFLD). In Wistar rats, NAFLD model was induced by 20 weeks of high-fat diet (HFD) feeding. Rolling and adhesion of leukocytes and tissue perfusion in hepatic microcirculation were examined using in vivo microscopic and laser speckle contrast imaging (LSCI), respectively. Oxidative stress and inflamatory parameters were analysed by TBARs, catalase enzyme activity, RT-PCR and ELISA. The participation of advanced glycation end-products (AGE) and its receptor RAGE was evaluated by the measurement of gene and protein expression of RAGE by RT-PCR and Western-blot, respectively and by liver and serum quantification of fluorescent AGEs. Wistar rats fed high-fat diet (HFD) showed increase in epididymal and abdominal fat content, systolic arterial blood pressure, fasting blood glucose levels, hepatic triglycerides and cholesterol, and impairment of glucose and insulin metabolisms. Liver histology confirmed the presence of steatosis and ultrasound analysis revealed increased liver size and parenchymal echogenicity in HFD-fed rats. HFD causes significant increases in leukocyte rolling and adhesion on hepatic microcirculation and decrease in liver microvascular blood flow. Liver tissue presented increase in oxidative stress and inflammtion. At 20 weeks, there was a significantly increase in AGE content in the liver and serum of HFD-fed rats and an increase in RAGE gene expression in the liver. The increase in liver AGE levels and microcirculatory disturbances could play a role in the pathogenesis of liver injury and are key components of NAFLD.

Similar to gestation/lactation, puberty is also a critical phase in which neuronal connections are still being produced and during which metabolic changes may occur if nutrition is disturbed. In the present study we aimed to determine whether peripubertal protein restriction induces metabolic programming. Thirty-day-old male rats were fed either a low protein (LP group) diet (4% w/w protein) or a normal protein (NP group) diet (23%) until 60 days of age, when they received the NP diet until they were 120 days old. Body weight (BW), food intake, fat tissue accumulation, glucose tolerance, and insulin secretion were evaluated. The nerve electrical activity was recorded to evaluate autonomous nervous system (ANS) function. Adolescent LP rats presented hypophagia and lower BW gain during the LP diet treatment (P<0.001). However, the food intake and BW gain by the LP rats were increased (P<0.001) after the NP diet was resumed. The LP rats presented mild hyperglycemia, hyperinsulinemia, severe hyperleptinemia upon fasting, peripheral insulin resistance and increased fat tissue accumulation and vagus nerve activity (P<0.05). Glucose-induced insulin secretion was greater in the LP islets than in the NP islets; however, the cholinergic response was decreased (P<0.05). Compared with the islets from the NP rats, the LP islets showed changes in the activity of muscarinic receptors (P<0.05); in addition, the inhibition of glucose-induced insulin secretion by epinephrine was attenuated (P<0.001). Protein restriction during adolescence caused high-fat tissue accumulation in adult rats. Islet dysfunction could be related to an ANS imbalance.

Metabolic malprogramming has been associated with low birth weight; however, the interplay between insulin secretion disruption and adrenal function upon lipid metabolism is unclear in adult offspring from protein-malnourished mothers during the last third of gestation. Thus, we aimed to study the effects of a maternal low-protein diet during the last third of pregnancy on adult offspring metabolism, including pancreatic islet function and morphophysiological aspects of the liver, adrenal gland, white adipose tissue, and pancreas. Virgin female Wistar rats (age 70 d) were mated and fed a protein-restricted diet (4%, intrauterine protein restricted [IUPR]) from day 14 of pregnancy until delivery, whereas control dams were fed a 20.5% protein diet. At age 91 d, their body composition, glucose-insulin homeostasis, ACTH, corticosterone, leptin, adiponectin, lipid profile, pancreatic islet function and liver, adrenal gland, and pancreas morphology were assessed. The birth weights of the IUPR rats were 20% lower than the control rats (P < .001). Adult IUPR rats were heavier, hyperphagic, hyperglycemic, hyperinsulinemic, hyperleptinemic, and hypercorticosteronemic (P < .05) with higher low-density lipoprotein cholesterol and lower high-density lipoprotein cholesterol, adiponectin, ACTH, and insulin sensitivity index levels (P < .01). The insulinotropic action of glucose and acetylcholine as well as muscarinic and adrenergic receptor function were impaired in the IUPR rats (P < .05). Maternal undernutrition during the last third of gestation disrupts the pancreatic islet insulinotropic response and induces obesity-associated complications. Such alterations lead to a high risk of metabolic syndrome, characterized by insulin resistance, visceral obesity, and lower high-density lipoprotein cholesterol.

Background/ Aims : Impaired pancreatic beta cell function and insulin secretion/action are a link between obesity and type 2 diabetes, which are worldwide public health burdens. We aimed to characterize the muscarinic acetylcholine receptor (mAChR) M₁-M₄ subtypes in isolated pancreatic islets from pre-diabetic obese rats that had been treated neonatally with monosodium L-glutamate (MSG). Methods : At 90 days of age, both the MSG and the control groups underwent biometric and biochemical evaluation. Anti-muscarinic drugs were used to study mAChR function either in vivo or in vitro. Results : The results demonstrated that atropine treatment reduced insulin secretion in the MSG-treated and control groups, whereas treatment with an M₂mAChR-selective antagonist increased secretion. Moreover, the insulinostatic effect of an M₃mAChR-selective antagonist was significantly higher in the MSG-treated group. M₁mAChR and M₃mAChR expression was increased in the MSG-obese group by 55% and 73%, respectively. In contrast, M₂mAChR expression decreased by 25% in the MSG group, whereas M₄mAChR expression was unchanged. Conclusions : Functional changes in and altered content of the mAChR (M₁-M₄) subtypes are pivotal to the demand for high pancreatic beta cell insulin secretion in MSG-obese rats, which is directly associated with vagal hyperactivity and peripheral insulin resistance.

We examined the long-term effects of protein restriction during puberty on the function of hypothalamic–pituitary–adrenal (HPA) and hypothalamic–pituitary–gonadal (HPG) axes in male rats. Male Wistar rats from the age of 30 to 60 days were fed a low-protein diet (4%, LP). A normal-protein diet (20.5%) was reintroduced to rats from the age of 60 to 120 days. Control rats were fed a normal-protein diet throughout life (NP). Rats of 60 or 120 days old were killed. Food consumption, body weight, visceral fat deposits, lipid profile, glycemia, insulinemia, corticosteronemia, adrenocorticotropic hormone (ACTH), testosteronemia and leptinemia were evaluated. Glucose-insulin homeostasis, pancreatic-islet insulinotropic response, testosterone production and hypothalamic protein expression of the androgen receptor (AR), glucocorticoid receptor (GR) and leptin signaling pathway were also determined. LP rats were hypophagic, leaner, hypoglycemic, hypoinsulinemic and hypoleptinemic at the age of 60 days (P < 0.05). These rats exhibited hyperactivity of the HPA axis, hypoactivity of the HPG axis and a weak insulinotropic response (P < 0.01). LP rats at the age of 120 days were hyperphagic and exhibited higher visceral fat accumulation, hyperleptinemia and dyslipidemia; lower blood ACTH, testosterone and testosterone release; and reduced hypothalamic expression of AR, GR and SOCS3, with a higher pSTAT3/STAT3 ratio (P < 0.05). Glucose-insulin homeostasis was disrupted and associated with hyperglycemia, hyperinsulinemia and increased insulinotropic response of the pancreatic islets. The cholinergic and glucose pancreatic-islet responses were small in 60-day-old LP rats but increased in 120-day-old LP rats. The hyperactivity of the HPA axis and the suppression of the HPG axis caused by protein restriction at puberty contributed to energy and metabolic disorders as long-term consequences.