Pancreatic functions in high salt fed female rats

Altered gut microbiome and autism like behavior are associated with parental high salt diet in male mice

Neurodevelopmental disorders are conditions caused by the abnormal development of the central nervous system. Autism spectrum disorder (ASD) is currently the most common form of such disorders, affecting 1% of the population worldwide. Despite its prevalence, the mechanisms underlying ASD are not fully known. Recent studies have suggested that the maternal gut microbiome can have profound effects on neurodevelopment. Considering that the gut microbial composition is modulated by diet, we tested the hypothesis that ASD-like behavior could be linked to maternal diet and its associated gut dysbiosis. Therefore, we used a mouse model of parental high salt diet (HSD), and specifically evaluated social and exploratory behaviors in their control-fed offspring. Using 16S genome sequencing of fecal samples, we first show that (1) as expected, HSD changed the maternal gut microbiome, and (2) this altered gut microbiome was shared with the offspring. More importantly, behavioral analysis of the offspring showed hyperactivity, increased repetitive behaviors, and impaired sociability in adult male mice from HSD-fed parents. Taken together, our data suggests that parental HSD consumption is strongly associated with offspring ASD-like behavioral abnormalities via changes in gut microbiome.

Dietary sodium chloride attenuates increased β-cell mass to cause glucose intolerance in mice under a high-fat diet

Excessive sodium salt (NaCl) or fat intake is associated with a variety of increased health risks. However, whether excessive NaCl intake accompanied by a high-fat diet (HFD) affects glucose metabolism has not been elucidated. In this study, C57BL/6J male mice were fed a normal chow diet (NCD), a NCD plus high-NaCl diet (NCD plus NaCl), a HFD, or a HFD plus high-NaCl diet (HFD plus NaCl) for 30 weeks. No significant differences in body weight gain, insulin sensitivity, and glucose tolerance were observed between NCD-fed and NCD plus NaCl-fed mice. In contrast, body and liver weights were decreased, but the weight of epididymal white adipose tissue was increased in HFD plus NaCl-fed compared to HFD-fed mice. HFD plus NaCl-fed mice had lower plasma glucose levels in an insulin tolerance test, and showed higher plasma glucose and lower plasma insulin levels in an intraperitoneal glucose tolerance test compared to HFD-fed mice. The β-cell area and number of islets were decreased in HFD plus NaCl-fed compared to HFD-fed mice. Increased Ki67-positive β-cells, and increased expression levels of Ki67, CyclinB1, and CyclinD1 mRNA in islets were observed in HFD-fed but not HFD plus NaCl-fed mice when compared to NCD-fed mice. Our data suggest that excessive NaCl intake accompanied by a HFD exacerbates glucose intolerance, with impairment in insulin secretion caused by the attenuation of expansion of β-cell mass in the pancreas.

Intermittent Fasting for Twelve Weeks Leads to Increases in Fat Mass and Hyperinsulinemia in Young Female Wistar Rats

Fasting is known to cause physiological changes in the endocrine pancreas, including decreased insulin secretion and increased reactive oxygen species (ROS) production. However, there is no consensus about the long-term effects of intermittent fasting (IF), which can involve up to 24 hours of fasting interspersed with normal feeding days. In the present study, we analyzed the effects of alternate-day IF for 12 weeks in a developing and healthy organism. Female 30-day-old Wistar rats were randomly divided into two groups: control, with free access to standard rodent chow; and IF, subjected to 24-hour fasts intercalated with 24-hours of free access to the same chow. Alternate-day IF decreased weight gain and food intake. Surprisingly, IF also elevated plasma insulin concentrations, both at baseline and after glucose administration collected during oGTT. After 12 weeks of dietary intervention, pancreatic islets displayed increased ROS production and apoptosis. Despite their lower body weight, IF animals had increased fat reserves and decreased muscle mass. Taken together, these findings suggest that alternate-day IF promote β -cell dysfunction, especially in developing animals. More long-term research is necessary to define the best IF protocol to reduce side effects.

Endurance exercise training restores diabetes-induced alteration in circulating Glycosylphosphatidylinositol-specific phospholipase D levels in rats

BACKGROUND

Glycosylphosphatidylinositol-specific phospholipase D (GPLD1) is responsible for cleaving membrane-associated glycosylphosphatidylinositol (GPI) molecules, which is affected by diabetes. We aimed to examine the effect of 14 weeks treadmill running on serum GPLD1 levels and its association with glycemic indexes and serum glypican-4 (GPC-4), a novel GPI-anchored adipokine, in streptozotocin-nicotinamide-induced diabetic rats.

METHODS

Thirty-six male Wister rats were randomly divided into three groups of twelve animals each, involving sedentary control (SC), sedentary diabetic (SD), and trained diabetic (TD) groups. The diabetes was induced through intraperitoneal injection of 120 mg/kg nicotinamide 15 min prior to intraperitoneal injection of 65 mg/kg streptozotocin in SD and TD groups. The TD group was exercised on a treadmill for 60 min/days, 5 days/wk at 26 m/min, and zero grade for 14 weeks. Following the experiment period, blood samples were taken from all animals and analyzed for experimental indexes via sandwich ELISA.

RESULTS

Exercise training caused a significant decrease in the elevated blood glucose levels and a significant increase in the lowered blood insulin levels in TD rats (both p < 0.001). Glucose tolerance of TD rats significantly improved following experimental protocol, as indicated by OGTT (p < 0.001). Experimental diabetes significantly increased serum GPLD1 levels (p < 0.001), while exercise training significantly decreased its levels (p < 0.001). Serum GPLD1 levels correlated directly with glycemic indexes involving FBS, 2hOGTT, and AUC of glucose (r = 0.80, r = 0.79, r = 0.79, respectively, all p < 0.001) and inversely with serum insulin levels (r = - 0.83, p < 0.001). There were no significant differences in serum GPC-4 levels among groups, and no association with GPLD1 alteration.

CONCLUSIONS

Sedentary diabetic rats have higher circulating GPLD1 compared to controls, which can be reversed by exercise training and is associated with modifying in glycemic and insulin profile.

The response of serum Glypican-4 levels and its potential regulatory mechanism to endurance training and chamomile flowers' hydroethanolic extract in streptozotocin-nicotinamide-induced diabetic rats

AIMS

Glypican-4 (GPC-4) is a novel adipomyokine that enhances insulin signaling. Glycosylphosphatidylinositol-specific phospholipase D (GPLD1) is thought to release GPC-4 and is itself an insulin-regulated enzyme. Beneficial effects of exercise training and chamomile flowers extract (CFE) are shown through activation of PPARγ, which is a promising drug target in diabetes and associated with GPC-4 synthesis. This study investigated the effects of 14-week treadmill running and CFE on serum GPC-4, GPLD1, and insulin levels in streptozotocin-nicotinamide (STZ-NA)-induced diabetic rats.

METHODS

Thirty-two STZ-NA-induced diabetic male Wistar rats were randomly assigned to four groups: control (C), training (T), CFE treatment (CFE), and training plus CFE treatment (TCFE) groups. The training groups were exercised on treadmill 5 days/week and the treating groups were fed with 200 mg/kg/day CFE in drinking water for 14 weeks. Finally, serum GPC-4, GPLD1, and insulin levels were analyzed via sandwich ELISA.

RESULTS

Compared to the control group, serum insulin levels were significantly higher in the T, CFE, and TCFE groups (p < 0.05, p < 0.05, p < 0.01, respectively), while OGTT and serum GPLD1 levels were significantly lower in the T, CFE, and TCFE groups (all p < 0.001). Changes in serum GPC-4 levels were not significant. Serum GPLD1 levels were negatively correlated with insulin levels and HOMA-IS (both p < 0.001).

CONCLUSIONS

This study suggests that endurance training and CFE may downregulate serum GPLD1 levels in STZ-NA-induced diabetic rats, which associate with the serum insulin profile. However, the results show that endurance training and CFE may not cause serum GPC-4 adaptation in STZ-NA-induced diabetic rats.

A high salt diet inhibits obesity and delays puberty in the female rat

BACKGROUND/OBJECTIVES

Processed foods are considered major contributors to the worldwide obesity epidemic. In addition to high sugar and fat contents, processed foods contain large amounts of salt. Owing to the correlations with rising adiposity, salt has recently been proposed to be obesogenic. This study investigated three hypotheses: (i) high salt contributes to weight gain and adiposity in juvenile female rats, (ii) puberty onset would be altered because salt is known to affect neuronal systems involved in activating the reproductive system, and (iii) enhanced adiposity will act synergistically with salt to drive early puberty onset.

DESIGN

Female weanling rats (post-natal day 21, n=105) were fed a low fat/low salt diet, low fat/high salt diet, high fat/low salt diet or a high salt/high fat diet for 24 days. Metabolic measures, including weight gain, food intake, fecal output, activity and temperature were recorded in subsets of animals.

RESULTS

Body weight, retroperitoneal and perirenal fat pad weight, and adipocyte size were all lower in animals fed high fat/high salt compared with animals fed high fat alone. Leptin levels were reduced in high fat/high salt fed animals compared with high fat/low salt-fed animals. Daily calorie intake was higher initially but declined with adjusted food intake and was not different among groups after 5 days. Osmolality and corticosterone were not different among groups. Fecal analysis showed excess fat excretion and a decreased digestive efficiency in animals fed high fat/low salt but not in animals fed high fat/high salt. Although respiratory exchange ratio was reduced by high dietary fat or salt, aerobic-resting metabolic rate was not affected by the diet. High salt delayed puberty onset, regardless of dietary fat content.

CONCLUSIONS

Salt delays puberty and prevents the obesogenic effect of a high fat diet. The reduced weight gain evident in high salt-fed animals is not due to differences in food intake or digestive efficiency.