Portal hypertensive cardiovascular pathology: the rescue of ancestral survival mechanisms?

Portal hypertension: The desperate search for the placenta

We propose that the circulatory impairments produced, in both portal hypertension and liver cirrhosis, to a certain degree resemble those characterizing prenatal life in the fetus. In fact, the left-right circulatory syndrome is common in cirrhotic patients and in the fetus. Thus, in patients with portal hypertension and chronic liver failure, the re-expression of a blood circulation comparable to fetal circulation is associated with the development of similar amniotic functions, i.e., ascites production and placenta functions, and portal vascular enteropathy. Therefore, these re-expressed embryonic functions are extra-embryonic and responsible for prenatal trophism and development.

Embrionary way to create a fatty liver in portal hypertension

Portal hypertension in the rat by triple partial portal vein ligation produces an array of splanchnic and systemic disorders, including hepatic steatosis. In the current review these alterations are considered components of a systemic inflammatory response that would develop through three overlapping phenotypes: The neurogenic, the immune and the endocrine. These three inflammatory phenotypes could resemble the functions expressed during embryonic development of mammals. In turn, the inflammatory phenotypes would be represented in the embryo by two functional axes, that is, a coelomic-amniotic axis and a trophoblastic yolk-sac or vitelline axis. In this sense, the inflammatory response developed after triple partial portal vein ligation in the rat would integrate both functional embryonic axes on the liver interstitial space of Disse. If so, this fact would favor the successive development of steatosis, steatohepatitis and fibrosis. Firstly, these recapitulated embryonic functions would produce the evolution of liver steatosis. In this way, this fat liver could represent a yolk-sac-like in portal hypertensive rats. After that, the systemic recapitulation of these embryonic functions in experimental prehepatic portal hypertension would consequently induce a gastrulation-like response in which a hepatic wound healing reaction or fibrosis occur. In conclusion, studying the mechanisms involved in embryonic development could provide key results for a better understanding of the nonalcoholic fatty liver disease etiopathogeny.

A computer model simulating human glucose absorption and metabolism in health and metabolic disease states

A computer model designed to simulate integrated glucose-dependent changes in splanchnic blood flow with small intestinal glucose absorption, hormonal and incretin circulation and hepatic and systemic metabolism in health and metabolic diseases e.g. non-alcoholic fatty liver disease, (NAFLD), non-alcoholic steatohepatitis, (NASH) and type 2 diabetes mellitus, (T2DM) demonstrates how when glucagon-like peptide-1, (GLP-1) is synchronously released into the splanchnic blood during intestinal glucose absorption, it stimulates superior mesenteric arterial (SMA) blood flow and by increasing passive intestinal glucose absorption, harmonizes absorption with its distribution and metabolism. GLP-1 also synergises insulin-dependent net hepatic glucose uptake (NHGU). When GLP-1 secretion is deficient post-prandial SMA blood flow is not increased and as NHGU is also reduced, hyperglycaemia follows. Portal venous glucose concentration is also raised, thereby retarding the passive component of intestinal glucose absorption.   Increased pre-hepatic sinusoidal resistance combined with portal hypertension leading to opening of intrahepatic portosystemic collateral vessels are NASH-related mechanical defects that alter the balance between splanchnic and systemic distributions of glucose, hormones and incretins.The model reveals the latent contribution of portosystemic shunting in development of metabolic disease. This diverts splanchnic blood content away from the hepatic sinuses to the systemic circulation, particularly during the glucose absorptive phase of digestion, resulting in inappropriate increases in insulin-dependent systemic glucose metabolism.  This hastens onset of hypoglycaemia and thence hyperglucagonaemia. The model reveals that low rates of GLP-1 secretion, frequently associated with T2DM and NASH, may be also be caused by splanchnic hypoglycaemia, rather than to intrinsic loss of incretin secretory capacity. These findings may have therapeutic implications on GLP-1 agonist or glucagon antagonist usage.

The wound-healing response and upregulated embryonic mechanisms: brothers-in-arms forever

The cutaneous wound-healing reaction occurs in overlapping but inter-related phases, which ultimately result in fibrosis. The pathophysiological mechanisms involved in fibrotic diseases, including organ-related and even systemic diseases, such as systemic sclerosis, could represent the successive systemic upregulation of extraembryonic-like phenotypes, that is, amniotic and vitelline phenotypes. These two extraembryonic-like phenotypes act on the injured tissue to induce a process similar to gastrulation, which occurs during the early phases of embryo development. The amniotic-like phenotype plays a leading role in the development of neurogenic responses with significant hydroelectrolytic alterations that essentially represent the development of open microcirculation within the injured tissue. In turn, through the overlapping expression of a vitelline-like phenotype, a bone marrow-related response is produced. Interstitial infiltration by molecular and cellular mediators contributed by amniotic- and vitelline-like functions provides the functional and metabolic autonomy needed for inducing new tissue formation through mechanisms similar to those that act in gastrulation during the early phases of embryonic development. Thus, while a new tissue is formed, it quickly evolves into fibrotic tissue because of premature senescence. Mechanisms related to extraembryonic-like functions have been suggested in the following physiological and pathological processes: embryonic development; wound-healing reactions occurring during adult life; and senescence. The existence of this sort of basic self-organizing fractal-like functional pattern is an essential characteristic of our way of life.

Endothelium dependent expression and underlying mechanisms of des-Arg⁹-bradykinin-induced B₁R-mediated vasoconstriction in rat portal vein

Endothelial dysfunction has been implicated in portal vein obstruction, a condition responsible for major complications in chronic portal hypertension. Increased vascular tone due to disruption of endothelial function has been associated with an imbalance in the equilibrium between endothelium-derived relaxing and contracting factors. Herein, we assessed underlying mechanisms by which expression of bradykinin B(1) receptor (B(1)R) is induced in the endothelium and how its stimulation triggers vasoconstriction in the rat portal vein. Prolonged in vitro incubation of portal vein resulted in time- and endothelium-dependent expression of B(1)R and cyclooxygenase-2 (COX-2). Inhibition of protein kinase C (PKC) or phosphatidylinositol 3-kinase (PI3K) significantly reduced expression of B(1)R through the regulation of transcription factors, activator protein-1 (AP-1) and cAMP response element-binding protein (CREB). Moreover, pharmacological studies showed that B(1)R-mediated portal vein contraction was reduced by COX-2, but not COX-1, inhibitors. Notably, activation of endothelial B(1)R increased phospholipase A(2)/COX-2-derived thromboxane A(2) (TXA(2)) levels, which in turn mediated portal vein contraction through binding to TXA(2) receptors expressed in vascular smooth muscle cells. These results provide novel molecular mechanisms involved in the regulation of B(1)R expression and identify a critical role for the endothelial B(1)R in the modulation of portal vein vascular tone. Our study suggests a potential role for B(1)R antagonists as therapeutic tools for diseases where portal hypertension may be involved.

A wound-like inflammatory aortic response in chronic portal hypertensive rats

Long-term prehepatic portal hypertension in the rat produces a low-grade splanchnic inflammation with liver steatosis and dyslipidemia. It has been suggested that in this experimental model these inflammatory alterations could represent a risk factor of vascular disease. Therefore, our aim was to investigate whether long-term prehepatic portal hypertension (PH) induces vascular pathology, fundamentally inflammatory aortopathy. Male Wistar sham-operated (SO) rats and rats with triple partial portal vein ligation in the very long-term (22 months) of postoperative evolution were used. Serum lipid profile, pro- and anti- inflammatory cytokines and ACTH and corticosterone were assayed by spectrophotometric and ELISA techniques. Aorta mRNA expression of oxidative and nitrosative stress enzymes, NFκB e IκB, immune-related cytokine production and vascular fibrosis parameters, were evaluated by real time RT-PCR. In addition, aortic p22phox subunit immunostaining, morphometry and vascular fibrosis in aorta were analyzed. PH rats have increased serum cholesterol, triglyceride, low-density lipoproteins (LDL) and very low-density lipoproteins (VLDL), while high-density lipoproteins (HDL) were lower than in SO rats. Serum ACTH and corticosterone decreased in PH rats. Also, serum TNF-α, IL-1β and IL-6 were significantly higher in PH-rats. Portal hypertensive-rats showed aortic oxidative stress with increased mRNA expressions of NAD(P)H oxidase p22phox, XDh, SOD and eNOS; higher aortic levels of pro-inflammatory cytokines, including TNF-α, IL-1β and IL-6; remodeling markers, like collagen I, CTGF and MMP-9; and finally, higher protein production of p22phox and collagen and extracellular matrix density were significantly higher in rats with PH. The results from the current study suggest that very long-term prehepatic portal hypertension in rats induces an abdominal aortic inflammatory and fibrotic response. Therefore, it could be considered that portal hypertension aggravates aortic inflammaging and one of its more severe complications, which is remodeling by a wound healing reaction.