Hepatocyte-Specific Deletion of Mouse Lamin A/C Leads to Male-Selective Steatohepatitis

BACKGROUND & AIMS

Lamins are nuclear intermediate filament proteins that comprise the major components of the nuclear lamina. Mutations in LMNA, which encodes lamins A/C, cause laminopathies, including lipodystrophy, cardiomyopathy, and premature aging syndromes. However, the role of lamins in the liver is unknown, and it is unclear whether laminopathy-associated liver disease is caused by primary hepatocyte defects or systemic alterations.

METHODS

To address these questions, we generated mice carrying a hepatocyte-specific deletion of Lmna (knockout [KO] mice) and characterized the KO liver and primary hepatocyte phenotypes by immunoblotting, immunohistochemistry, microarray analysis, quantitative real-time polymerase chain reaction, and Oil Red O and Picrosirius red staining.

RESULTS

KO hepatocytes manifested abnormal nuclear morphology, and KO mice showed reduced body mass. KO mice developed spontaneous male-selective hepatosteatosis with increased susceptibility to high-fat diet-induced steatohepatitis and fibrosis. The hepatosteatosis was associated with up-regulated transcription of genes encoding lipid transporters, lipid biosynthetic enzymes, lipid droplet-associated proteins, and interferon-regulated genes. Hepatic Lmna deficiency led to enhanced signal transducer and activator of transcription 1 (Stat1) expression and blocked growth hormone-mediated Janus kinase 2 (Jak2), signal transducer and activator of transcription 5 (Stat5), and extracellular signal-regulated kinase (Erk) signaling.

CONCLUSIONS

Lamin A/C acts cell-autonomously to maintain hepatocyte homeostasis and nuclear shape and buffers against male-selective steatohepatitis by positively regulating growth hormone signaling and negatively regulating Stat1 expression. Lamins are potential genetic modifiers for predisposition to steatohepatitis and liver fibrosis. The microarray data can be found in the Gene Expression Omnibus repository (accession number: GSE93643).

Health status and practices of urban Caribbean Latinos with diabetes mellitus

Although Caribbean Latinos are more likely than non-Hispanic whites to develop diabetes, their health status has been poorly characterized. Information on diabetes management, metabolic control, dietary habits, and diabetes knowledge was gathered from a group of urban Caribbean Latinos with diabetes in order to characterize the nutritional behaviors, diabetes attitudes, health perceptions, and metabolic control of this high risk group. Interviews and medical record reviews were conducted among seventy low-income urban Caribbean Latinos with type 2 diabetes mellitus. Patients attending outpatient clinics were interviewed by bilingual interviewers. Medical records were reviewed to ascertain prevalence of diabetes-related complications, medications, and metabolic parameters. Participants were primarily Spanish-speaking and of Puerto Rican origin. Eighty-one percent were unemployed, and only 27% had completed high school or higher educational levels. Average hemoglobin A1c was 10.6%. Among those with hypertension and hyperlipidemia, many were not receiving treatment. Participants' estimation of their own degree of metabolic control was poor, as was their understanding of desirable blood glucose and weight goals. A second evening meal was common. Diets were higher in fat and sugar content than currently recommended. More effective treatment strategies for both patients and providers are needed to improve glycemic control and cardiovascular risk factors among indigent urban Caribbean Latinos. Essential features of such strategies for patient programs include culturally appropriate dietary counseling and low literacy materials to better communicate glycemic and weight goals and dietary guidelines. Provider education is needed regarding established guidelines and cultural influences on diabetes-related practices.