Human liver afferent and efferent nerves revealed by 3-D/Airyscan super-resolution imaging

Metabolic syndrome traits differentially and cumulatively influence micro- and macrovascular disease risk in patients with MASLD

INTRODUCTION

The cumulative impact of metabolic syndrome (MetS) components on micro- and macrovascular disease in metabolic dysfunction-associated steatotic liver disease (MASLD) is unclear. We aimed to determine whether the number of the MetS components increases the risk of micro- and macrovascular disease in patients with MASLD.

METHODS

We performed a retrospective cohort study of electronic medical records using the TriNetX network, a global federated database. The exposure arm was patients with hepatic steatosis (defined via International Classification of Diseases, 10th Revision coding, or modified hepatic steatosis index), and ≥1 MetS components (obesity/central adiposity, insulin resistance, hypertension, or dyslipidaemia), compared with a reference arm of adults without any MetS components or hepatic steatosis. Our propensity score matched (1:1) for confounders with 5 years of follow-up. Primary outcomes included microvascular (peripheral neuropathy, retinopathy, and nephropathy) and macrovascular (cardiovascular events, cerebrovascular accidents, and peripheral vascular disease) disease. Secondary analyses assessed the impact of additional MetS components on these outcomes, as well as the impact of sex.

RESULTS

MASLD, defined by hepatic steatosis and insulin resistance (n = 15 937), carried the highest risk of microvascular disease (HR 13.93 (95% CI 8.55-22.68)), whilst MASLD, defined by hepatic steatosis and hypertension (n = 53 028), carried the highest risk of macrovascular disease (7.23 (6.45-8.13)). MASLD with all MetS components carried greatest risk of both micro- (31.20 (28.88-33.70) (n = 462 789)) and macrovascular (8.04 (7.33-8.82) (n = 336 010)) disease.

CONCLUSION

We demonstrate a differential effect of MetS components on micro- and macrovascular disease risk in patients with MASLD, with a cumulative impact of multiple MetS on overall risk. The impact of MetS components was most pronounced in women. Aggressive metabolic risk factor management is critical for prevention of micro- and macrovascular complications.

Liver adrenoceptor alpha-1b plays a key role in energy and glucose homeostasis in female mice

The liver plays a major role in glucose and lipid homeostasis and acts as a key organ in the pathophysiology of metabolic diseases. Intriguingly, increased sympathetic nervous system (SNS) activity to the liver has been associated with the development and progression of type 2 diabetes and obesity. However, the precise mechanisms by which the SNS regulates hepatic metabolism remain to be defined. Although liver α1-adrenoceptors were suggested to play a role in glucose homeostasis, the specific subtypes involved are unknown mainly because of the limitations of pharmacological tools. Here, we generated and validated a novel mouse model allowing tissue-specific deletion of α-1b adrenoceptor (Adra1b) in hepatocytes to investigate the role of liver ADRA1B in energy and glucose metabolism. We found that selective deletion of Adra1b in mouse liver has limited metabolic impact in lean mice. However, loss of Adra1b in hepatocytes exacerbated diet-induced obesity, insulin resistance, and glucose intolerance in female, but not in male mice. In obese females, this was accompanied by reduced hepatic gluconeogenic capacity and reprogramming of gonadal adipose tissue with hyperleptinemia. Our data highlight sex-dependent mechanisms by which the SNS regulates energy and glucose homeostasis through liver ADRA1B.NEW & NOTEWORTHY The sympathetic nervous system plays an important role in regulating hepatic physiology and metabolism. However, the identity of the adrenoceptors involved in these effects is still elusive. Using CRISPR-Cas9, we developed a novel transgenic tool to study the role of liver α-1b adrenoceptor (ADRA1B). We show that ADRA1B plays a key role in mediating the effects of the sympathetic nervous system on hepatic metabolism, particularly in female mice.

Pelvic neural injuries and acute voiding changes in rat models of radical hysterectomy

OBJECTIVE

To establish experimental models of radical hysterectomy based on Querleu-Morrow classification, and clarify the quantitative evaluation of pelvic neural injuries and acute voiding changes postoperatively.

METHODS

Female Sprague Dawley rats were randomized and received sham operation, type A, B1, C1 and C2 radical hysterectomies (as the injury gradually increased), respectively. The excised specimens were collected for hematoxylin and eosin staining and Pgp9.5 (pan-neuronal marker) immunohistochemistry to evaluate the facial and neural resection of paracervix. At 21 days after operation, 5 rats in each group were used for urine spot test, awake cystometry and leak point pressure test, and the other 5 ones were used for hematoxylin and eosin staining of bladder and pelvic neural plane, and Masson's trichrome staining of bladder.

RESULTS

Paracervical Pgp9.5 immunohistochemistry revealed that the resected neural area in C2 group was significantly larger than that in type A, B1, and C1 groups. Compared with type A and B1 groups, the excised paracervical facial area was significant higher in type C1 and C2 groups. The occurrence of urinary retention was 0%, 10%, 40% and 100% in type A, B1, C1 and C2 groups, respectively, which was further confirmed by average residual volume. The incidence of neurogenic bladder and its severity gradually increased from type A to type C2 groups, consistent with the findings of leakage point pressure, bladder size, bladder weight, pathological changes and collagen deposition. Neuropathological evaluation revealed neural injuries involved the main components of pelvic neural plane.

CONCLUSION

The novel rat models of radical hysterectomy based on Querleu-Morrow classification revealed the structural and functional changes of voiding after operation, which reflected the situation in humans.

The development of hepatic steatosis depends on the presence of liver-innervating parasympathetic cholinergic neurons in mice fed a high-fat diet

Hepatic lipid metabolism is regulated by the autonomic nervous system of the liver, with the sympathetic innervation being extensively studied, while the parasympathetic efferent innervation is less understood despite its potential importance. In this study, we investigate the consequences of disrupted brain-liver communication on hepatic lipid metabolism in mice exposed to obesogenic conditions. We found that a subset of hepatocytes and cholangiocytes are innervated by parasympathetic nerve terminals originating from the dorsal motor nucleus of the vagus. The elimination of the brain-liver axis by deleting parasympathetic cholinergic neurons innervating the liver prevents hepatic steatosis and promotes browning of inguinal white adipose tissue (ingWAT). The loss of liver-innervating cholinergic neurons increases hepatic Cyp7b1 expression and fasting serum bile acid levels. Furthermore, knockdown of the G protein-coupled bile acid receptor 1 gene in ingWAT reverses the beneficial effects of the loss of liver-innervating cholinergic neurons, leading to the reappearance of hepatic steatosis. Deleting liver-innervating cholinergic neurons has a small but significant effect on body weight, which is accompanied by an increase in energy expenditure. Taken together, these data suggest that targeting the parasympathetic cholinergic innervation of the liver is a potential therapeutic approach for enhancing hepatic lipid metabolism in obesity and diabetes.

Hepatic noradrenergic innervation acts via CREB/CRTC2 to activate gluconeogenesis during cold

BACKGROUND AND AIM

Although it is well established that hormones like glucagon stimulates gluconeogenesis via the PKA-mediated phosphorylation of CREB and dephosphorylation of the cAMP-regulated CREB coactivators CRTC2, the role of neural signals in the regulation of gluconeogenesis remains uncertain.

METHODS AND RESULTS

Here, we characterize the noradrenergic bundle architecture in mouse liver; we show that the sympathoexcitation induced by acute cold exposure promotes hyperglycemia and upregulation of gluconeogenesis via triggering of the CREB/CRTC2 pathway. Following its induction by dephosphorylation, CRTC2 translocates to the nucleus and drives the transcription of key gluconeogenic genes. Rodents submitted to different models of sympathectomy or knockout of CRTC2 do not activate gluconeogenesis in response to cold. Norepinephrine directly acts in hepatocytes mainly through a Ca2+-dependent pathway that stimulates CREB/CRTC2, leading to activation of the gluconeogenic program.

CONCLUSION

Our data demonstrate the importance of the CREB/CRTC2 pathway in mediating effects of hepatic sympathetic inputs on glucose homeostasis, providing new insights into the role of norepinephrine in health and disease.