Randomised clinical study: acute effects of metformin versus placebo on portal pressure in patients with cirrhosis and portal hypertension

Pathophysiology and therapeutic options for cirrhotic portal hypertension

Portal hypertension represents the primary non-neoplastic complication of liver cirrhosis and has life-threatening consequences, such as oesophageal variceal bleeding, ascites, and hepatic encephalopathy. Portal hypertension occurs due to increased resistance of the cirrhotic liver vasculature to portal blood flow and is further aggravated by the hyperdynamic circulatory syndrome. Existing knowledge indicates that the profibrogenic phenotype acquired by sinusoidal cells is the initial factor leading to increased hepatic vascular tone and fibrosis, which cause increased vascular resistance and portal hypertension. Data also suggest that the phenotype of hepatic cells could be further impaired due to the altered mechanical properties of the cirrhotic liver itself, creating a deleterious cycle that worsens portal hypertension in the advanced stages of liver disease. In this Review, we discuss recent discoveries in the pathophysiology and treatment of cirrhotic portal hypertension, a condition with few pharmacological treatment options.

Metformin and the Liver: Unlocking the Full Therapeutic Potential

Metformin is a highly effective medication for managing type 2 diabetes mellitus. Recent studies have shown that it has significant therapeutic benefits in various organ systems, particularly the liver. Although the effects of metformin on metabolic dysfunction-associated steatotic liver disease and metabolic dysfunction-associated steatohepatitis are still being debated, it has positive effects on cirrhosis and anti-tumoral properties, which can help prevent the development of hepatocellular carcinoma. Furthermore, it has been proven to improve insulin resistance and dyslipidaemia, commonly associated with liver diseases. While more studies are needed to fully determine the safety and effectiveness of metformin use in liver diseases, the results are highly promising. Indeed, metformin has a terrific potential for extending its full therapeutic properties beyond its traditional use in managing diabetes.

Genetically Proxied Therapeutic Effect of Metformin Use, Blood Pressure, and Hypertension's Risk: a Drug Target-Based Mendelian Randomization Study

In this work, we aim to evaluate the association of the genetically proxied effect of metformin on blood pressure (BP) and hypertension through a drug target-based Mendelian randomization (MR) analysis. Thirty-two instrumental variables for five metformin targets (i.e., AMP-activated protein kinase (AMPK), growth differentiation factor 15 (GDF15), mitochondrial glycerol 3 (MG3), mitochondrial complex I (MCI), and glucagon (GCG)) were introduced to the MR analysis on the datasets of hypertension, systolic and diastolic blood pressure (SBP and DBP). The MR analyses demonstrated that the MCI- and MG3-specific metformin's use would significantly reduce SBP, DBP, and hypertension risk. The meta-analyses showed that the genetically proxied metformin's use equivalent to a 6.75 mmol/mol reduction on HbA1c could decrease both the SBP (beta =  - 1.05, P < 0.001) and DBP (beta =  - 0.51, P = 0.096). Furthermore, metformin's use was also implied to reduce the hypertension risk. The MG3- and MCI-dependent metformin's effect may play key roles in the anti-hypertension function.

Emerging Therapeutic Targets for Portal Hypertension

Purpose of Review

Portal hypertension is responsible of the main complications of cirrhosis, which carries a high mortality. Recent treatments have improved prognosis, but this is still far from ideal. This paper reviews new potential therapeutic targets unveiled by advances of key pathophysiologic processes.

Recent Findings

Recent research highlighted the importance of suppressing etiologic factors and a safe lifestyle and outlined new mechanisms modulating portal pressure. These include intrahepatic abnormalities linked to inflammation, fibrogenesis, vascular occlusion, parenchymal extinction, and angiogenesis; impaired regeneration; increased hepatic vascular tone due to sinusoidal endothelial dysfunction with insufficient NO availability; and paracrine liver cell crosstalk. Moreover, pathways such as the gut-liver axis modulate splanchnic vasodilatation and systemic inflammation, exacerbate liver fibrosis, and are being targeted by therapy. We have summarized studies of new agents addressing these targets.

Summary

New agents, alone or in combination, allow acting in complementary mechanisms offering a more profound effect on portal hypertension while simultaneously limiting disease progression and favoring regression of fibrosis and of cirrhosis. Major changes in treatment paradigms are anticipated.

Metformin Stimulates Intestinal Glycolysis and Lactate Release: A single-Dose Study of Metformin in Patients With Intrahepatic Portosystemic Stent

The pharmacodynamic effects of metformin remain elusive, but several lines of evidence suggest a critical role of direct effects in the gastrointestinal (GI) tract. We investigated if metformin stimulates intestinal glucose metabolism and lactate release in the prehepatic circulation. We included eight patients with transjugular intrahepatic portosytemic stent in an open label study. Portal and arterialized peripheral blood was obtained before and 90 minutes after ingestion of 1,000 mg metformin. Metformin increased lactate concentrations by 23% (95% confidence interval (CI): 6-40) after 90 minutes in the portal vein. The plasma concentration of glucose, insulin, and C-peptide was higher in the portal vein compared with arterialized blood (P < 0.05, all) and was lowered at both sampling sites following metformin ingestion (P < 0.01, all). Plasma concentration of GLP-1 was 20% (95% CI: 2-38) higher in the portal vein at baseline and metformin increased the concentration with 11% (1.5 pM, P = 0.05). The median concentration of growth differentiation factor 15 was 10% (95% CI: 1-19) higher in the portal vein compared with arterialized blood. Ninety minutes after metformin administration, the median portal vein concentration increased to around 3,000 ng/mL with a mean portal/arterial ratio of 1.5 (95% CI: 1.2-1.8). Non-targeted metabolomics showed that metformin acutely affected benzoate-hippurate metabolism. A single-dose of metformin directly affects substrate metabolism in the upper GI tract in humans with direct stimulation of nonoxidative glucose metabolism. These data suggest glucose lowering effects of metformin can be intrinsically linked with the GI tract without hepatic uptake of the drug.