IGF-1 receptor haploinsufficiency leads to age-dependent development of metabolic syndrome

IGF1R is a mediator of sex-specific metabolism in mice: Effects of age and high-fat diet

OBJECTIVE

We aimed to investigate the short and long-term metabolic consequences of IGF1R systemic gene deficiency in mice.

METHODS

UBC-CreERT2, Igf1r^fl/fl mutant mice were used to suppress IGF1R signaling in adult tissues by inducing postnatal generalized Igf1r deletion with tamoxifen. Animals were analyzed at two different ages: i) 13-weeks old young mice, and ii) 12-months old middle-aged mice. In addition, the effects of 10 weeks-long high-fat diet (HFD) were investigated in middle-aged mice.

RESULTS

Young IGF1R-deficient mice were insulin-resistant, with high IGF1, growth hormone (GH) and IGFBP3, as well as low IGFBP2 circulating levels. Males also presented increased triglycerides in liver. In contrast, middle-aged mice did not clearly show all of these alterations, suggesting possible compensatory effects. Middle-aged IGF1R-deficient male mice were able to counteract the negative effects induced by aging and HFD in adiposity, inflammation and glucose metabolism. A metabolic sexual dimorphism dependent on IGF1R was observed, especially in middle-aged mice.

CONCLUSIONS

These results demonstrate that IGF1R is involved in metabolic homeostasis, with effects modulated by diet-induced obesity and aging in a sex dependent manner. Thus, IGF1R deficiency in mice is proposed as a useful tool to understand metabolic alterations observed in patients with IGF1R gene deletions.

Insulin-Like Growth Factor I Regulation and Its Actions in Skeletal Muscle

The insulin-like growth factor (IGF) pathway is essential for promoting growth and survival of virtually all tissues. It bears high homology to its related protein insulin, and as such, there is an interplay between these molecules with regard to their anabolic and metabolic functions. Skeletal muscle produces a significant proportion of IGF-1, and is highly responsive to its actions, including increased muscle mass and improved regenerative capacity. In this overview, the regulation of IGF-1 production, stability, and activity in skeletal muscle will be described. Second, the physiological significance of the forms of IGF-1 produced will be discussed. Last, the interaction of IGF-1 with other pathways will be addressed. © 2019 American Physiological Society. Compr Physiol 9:413-438, 2019.

Identification of differential gene expression profile from peripheral blood cells of military pilots with hypertension by RNA sequencing analysis

Background

Elevated blood pressure is an important risk factor for cardiovascular disease and is also an important factor in global mortality. Military pilots are at high risk of cardiovascular disease because they undergo persistent noise, high mental tension, high altitude hypoxia, high acceleration and high calorie diet. Hypertension is the leading cause of cardiovascular disease in military pilots. In this study, we want to identify key genes from peripheral blood cells of military pilots with hypertension. Identification of these genes may help diagnose and control hypertension and extend flight career for military pilots.

Methods

We use RNA sequencing technology, bioinformatics analysis and Western blotting to identify key genes from peripheral blood cells of military pilots with hypertension.

Results

Our study detected 121 up-regulated genes and 623 down-regulated genes in the peripheral blood mononuclear cells (PBMCs) from hypertensive military pilots. We have also identified 8 important genes (NME4, PNPLA7, GGT5, PTGS2, IGF1R, NT5C2, ENTPD1 and PTEN), a number of gene ontology categories and biological pathways that may be associated with military pilot hypertension.

Conclusions

Our study may provide effective means for the prevention, diagnosis and treatment of hypertension for military pilot and extend their flight career.

Electronic supplementary material

The online version of this article (10.1186/s12920-018-0378-2) contains supplementary material, which is available to authorized users.

Increasing Cardiomyocyte Atrogin-1 Reduces Aging-Associated Fibrosis and Regulates Remodeling in Vivo

The muscle-specific ubiquitin ligase atrogin-1 (MAFbx) has been identified as a critical regulator of pathologic and physiological cardiac hypertrophy; it regulates these processes by ubiquitinating transcription factors [nuclear factor of activated T-cells and forkhead box O (FoxO) 1/3]. However, the role of atrogin-1 in regulating transcription factors in aging has not previously been described. Atrogin-1 cardiomyocyte-specific transgenic (Tg⁺) adult mice (α-major histocompatibility complex promoter driven) have normal cardiac function and size. Herein, we demonstrate that 18-month-old atrogin-1 Tg⁺ hearts exhibit significantly increased anterior wall thickness without functional impairment versus wild-type mice. Histologic analysis at 18 months revealed atrogin-1 Tg⁺ mice had significantly less fibrosis and significantly greater nuclei and cardiomyocyte cross-sectional analysis. Furthermore, by real-time quantitative PCR, atrogin-1 Tg⁺ had increased Col 6a4, 6a5, 6a6, matrix metalloproteinase 8 (Mmp8), and Mmp9 mRNA, suggesting a role for atrogin-1 in regulating collagen deposits and MMP-8 and MMP-9. Because atrogin-1 Tg⁺ mice exhibited significantly less collagen deposition and protein levels, enhanced Mmp8 and Mmp9 mRNA may offer one mechanism by which collagen levels are kept in check in the aged atrogin-1 Tg⁺ heart. In addition, atrogin-1 Tg⁺ hearts showed enhanced FoxO1/3 activity. The present study shows a novel link between atrogin-1-mediated regulation of FoxO1/3 activity and reduced collagen deposition and fibrosis in the aged heart. Therefore, targeting FoxO1/3 activity via the muscle-specific atrogin-1 ubiquitin ligase may offer a muscle-specific method to modulate aging-related cardiac fibrosis.