Retroperitoneal adipose tissue denervation improves cardiometabolic and autonomic dysfunction in a high fat diet model

Mechanisms involved in cardiovascular and hydroelectrolytic changes in dehydrated high-fat-diet-fed rats

Obesity is increasingly prevalent worldwide, and climate change is exacerbating water shortages, leading to dehydration. Both obesity and dehydration cause increased arterial pressure (AP), fluid electrolytic imbalance, and neuroinflammation. Thus, the present study aimed to verify the changes in the cardiovascular system, hydroelectrolytic balance, and microglia and neuronal activation in rats fed with a high-fat diet (HFD) in response to 24 h of water deprivation (WD) and the possible mechanisms involved. Male Holtzman rats (290-310 g) were fed with a standard diet (SD, 10% calories from fat) or HFD (46% calories from fat) for 6 wk before the WD experiments. Compared with WD SD rats, WD HFD rats presented a greater c-Fos immunolabeling in the subfornical organ (SFO) and supraoptic nucleus and greater microglial activation in SFO. WD-induced water intake was lower in HFD rats than in SD rats. WD HFD rats presented greater antidiuresis and lesser natriuresis than WD SD rats. Renal denervation did not change the antidiuresis or natriuresis observed in WD HFD- or SD-fed rats. The lower water intake in WD HFD rats might be due to neuroinflammation and/or decreased urinary output. The increase in AP after WD was similar between HFD and SD, but it is more dependent on angiotensin II type 1 (AT1) receptor activation in HFD rats. Overall, HFD rats seem less responsive to fluid and electrolyte balance responses to WD, highlighting the need for strategies to prevent dehydration in individuals with obesity, particularly during rising drought conditions worldwide.NEW & NOTEWORTHY Obesity and dehydration are common worldwide. Our study with an animal model found that changes in arterial pressure are linked to increased activation of the AT1 receptor in obese, dehydrated rats. The renal nerves appear unrelated to the significant decrease in urinary volume and sodium excretion in these animals. Neuroinflammation and reduced urine output may explain their lower water intake. These findings highlight the need for strategies to prevent dehydration in individuals with obesity.

Effects of a high-fat diet on gut microbiota and possible implications for bone health in male Wistar rats

Diet plays an important role in the composition of gut microbiota. Emerging research suggests that bone homeostasis can also be influenced by the gut microbiota. The aim of this study was to assess possible alterations in gut microbiota in an experimental obesity model induced by a high-fat diet (HFD) and the possible effects on parameters of bone metabolism and remodeling. Male Wistar rats were fed a HFD (60% lipids) or standard (control) diet for 14 weeks. Biochemical and hormonal parameters, bone histomorphometry, bone protein levels, and gut microbiota composition were analyzed. HFD animals exhibited a greater gut microbiota α-diversity represented by the Shannon Index and an increased relative abundance of the Proteobacteria phylum. Histomorphometry detected lower bone formation in the HFD group, accompanied by increased levels of serum and bone leptin and FGF-23 (fibroblast growth factor-23). The Shannon Index was correlated directly with bone FGF-23 (R 0.96, p = 0.04) and inversely with the osteoblastic surface (R -0.95, p = 0.04). The present study disclosed a significant increase in gut microbiota α-diversity and relative abundance of Proteobacteria phylum in obese animals fed a high-fat diet in parallel with increased levels of bone and serum leptin and FGF-23 and lower bone formation. The associations of Shannon Index with bone levels of FGF-23 and reduced osteoblastic surface suggest a link between HFD-induced higher gut microbiota diversity and low bone formation.

The Interplay between Liver and Adipose Tissue in the Onset of Liver Diseases: Exploring the Role of Vitamin Deficiency

The deficiency of vitamins, a condition known as "hidden hunger", causes comprehensive pathological states. Research over the years has identified a relationship between liver diseases and hypovitaminosis or defects in vitamin metabolism. The exact mechanisms remain elusive; however, the crucial involvement of specific vitamins in metabolic functions, alongside the reclassification of liver disease as metabolic dysfunction-associated steatotic liver disease (MASLD), has prompted researchers to investigate the potential cause-effect dynamics between vitamin deficiency and liver disease. Moreover, scientists are increasingly investigating how the deficiency of vitamins might disrupt specific organ crosstalk, potentially contributing to liver disease. Although the concept of a dysmetabolic circuit linking adipose tissue and the liver, leading to liver disease, has been discussed, the possible involvement of vitamin deficiency in this axis is a relatively recent area of study, with numerous critical aspects yet to be fully understood. In this review, we examine research from 2019 to July 2024 focusing on the possible link between liver-adipose tissue crosstalk and vitamin deficiency involved in the onset and progression of non-alcoholic fatty liver disease (NAFLD). Studies report that vitamin deficiency can affect the liver-adipose tissue axis, mainly affecting the regulation of systemic energy balance and inflammation.

Blockade of mesenteric and omental adipose tissue sensory neurons improves cardiac remodeling through sympathetic pathway

Mesenteric and omental adipose tissue (MOAT) communicates directly with the heart through the secretion of bioactive molecules and indirectly through afferent signaling to the central nervous system. Myocardial infarction (MI) may induce pathological alterations in MOAT, which further affects cardiac function. Our study revealed that MI induced significant MOAT transcriptional changes in genes related with signal transduction, including adiponectin (APN), neuropeptide Y (NPY), and complement C3 (C3), potentially influencing afferent activity. We further found that MOAT sensory nerve denervation with capsaicin (CAP) prevented cardiac remodeling, improved cardiac function, and reversed cardiac sympathetic nerve hyperactivation in the MI group, accompanied by reduced serum norepinephrine. In addition, CAP reversed the elevated MOAT afferent input and brain-heart sympathetic outflow post-MI, increasing APN and NPY and decreasing C3 and serum proinflammatory factors. These results demonstrated that blockade of the MOAT afferent sensory nerve exerts a cardioprotective effect by inhibiting the brain-heart sympathetic axis.

NMR metabolomics study of chronic low-dose exposure to a cocktail of persistent organic pollutants

Nowadays, exposure to endocrine-disrupting chemicals (EDCs), including persistent organic pollutants (POPs), is one of the most critical threats to public health. EDCs are chemicals that mimic, block, or interfere with hormones in the body's endocrine system and have been associated with a wide range of health issues. This innovative, untargeted metabolomics study investigates chronic low-dose internal exposure to a cocktail of POPs on multiple tissues that are known to accumulate these lipophilic compounds. Interestingly, the metabolic response differs among selected tissues/organs in mice. In the liver, we observed a dynamic effect according to the exposure time and the doses of POPs. In the brain tissue, the situation is the opposite, leading to the conclusion that the presence of POPs immediately gives a saturated effect that is independent of the dose and the duration of exposure studied. By contrast, for the adipose tissues, nearly no effect is observed. This metabolic profiling leads to a holistic and dynamic overview of the main metabolic pathways impacted in lipophilic tissues by a cocktail of POPs.

Adipose Tissue Denervation Blunted the Decrease in Bone Formation Promoted by Obesity in Rats

The impact of obesity upon bone metabolism is controversial since both beneficial or harmful effects have been reported. Bone remodeling is modulated by the central nervous system through cytokines, hormones and neuromodulators. The present study aimed to evaluate the effects evoked by bilateral retroperitoneal white adipose tissue (rWAT) denervation (Dnx) upon bone mineral metabolism and remodeling in an experimental model of obesity in rats. Male Wistar rats were fed during 18 weeks with high-fat diet (HFD) or standard diet (SD) as controls, and rWAT Dnx or Sham surgery was performed at the 14th week. Biochemical and hormonal parameters, bone histomorphometry, rWAT and hypothalamus protein and gene expression were analyzed. The HFD group presented decreased bone formation parameters, increased serum and bone leptin and FGF23, increased serum and hypothalamic neuropeptide Y (NPY) and decreased serum 1,25-dihydroxyvitamin D3 and PTH. After rWAT Dnx, bone markers and histomorphometry showed restoration of bone formation, and serum and hypothalamic NPY decreased, without alteration in leptin levels. The present study shows that the denervation of rWAT improved bone formation in obese rats mediated by a preferential reduction in neurohormonal actions of NPY, emphasizing the relevance of the adipose tissue-brain-bone axis in the control of bone metabolism in obesity.

Depot- and diabetes-specific differences in norepinephrine-mediated adipose tissue angiogenesis, vascular tone, collagen deposition and morphology in obesity

AIMS

Norepinephrine (NE) is a known regulator of adipose tissue (AT) metabolism, angiogenesis, vasoconstriction and fibrosis. This may be through autocrine/paracrine effects on local resistance vessel function and morphology. The aims of this study were to investigate, in human subcutaneous and omental adipose tissue (SAT and OAT): NE synthesis, angiogenesis, NE-mediated arteriolar vasoconstriction, the induction of collagen gene expression and its deposition in non-diabetic versus diabetic obese subjects.

MATERIALS AND METHODS

SAT and OAT from obese patients were used to investigate tissue NE content, tyrosine hydroxylase (TH) density, angiogenesis including capillary density, angiogenic capacity and angiogenic gene expression, NE-mediated arteriolar vasoconstriction and collagen deposition.

KEY FINDINGS

In the non-diabetic group, NE concentration, TH immunoreactivity, angiogenesis and maximal vasoconstriction were significantly higher in OAT compared to SAT (p < 0.05). However, arterioles from OAT showed lower NE sensitivity compared to SAT (10^-8 M to 10^-7.5 M, p < 0.05). A depot-specific difference in collagen deposition was also observed, being greater in OAT than SAT. In the diabetic group, no significant depot-specific differences were seen in NE synthesis, angiogenesis, vasoconstriction or collagen deposition. SAT arterioles showed significantly lower sensitivity to NE (10^-8 M to 10^-7.5 M, p < 0.05) compared to the non-diabetic group.

SIGNIFICANCE

SAT depot in non-diabetic obese patients exhibited relatively low NE synthesis, angiogenesis, tissue fibrosis and high vasoreactivity, due to preserved NE sensitivity. The local NE synthesis in OAT and diabetes desensitizes NE-induced vasoconstriction, and may also explain the greater tissue angiogenesis and fibrosis in these depots.