Essential roles of insulin, AMPK signaling and lysyl and prolyl hydroxylases in the biosynthesis and multimerization of adiponectin

Association of Serum Leptin and Adiponectin Concentrations with Type 2 Diabetes Biomarkers and Complications Among Saudi Women

Objective

Hyperglycemia and insulin resistance (IR) put obese women with Type 2 diabetes mellitus (T2DM) at risk for cardiovascular disease (CVD).

Methods

150 T2DM women aged 30-45 were studied cross-sectionally at Madinah Hospital lab to find T2DM risk factors and their association with adiponectin/leptin levels.

Results

Women with T2DM showed greater fasting blood glucose (FBG), hemoglobin A1c (HbA1c), triglycerides (TG), body mass index (BMI), waist circumference (WC), insulin resistance (IR), high-sensitivity C-reactive protein (hs-CRP), and CVD risk (high atherogenic index of plasma (AIP) and leptin), but decreased high-density lipoprotein (HDL-cholesterol) and poor insulin sensitivity with low adiponectin. Obese women with T2DM had increased leptin and reduced adiponectin. Leptin levels were significantly related to IR, BMI, and AIP (B= 3.97, P= 0.02) but not WC. Leptin levels were negatively correlated with insulin sensitivity (IS) and HDL-c (P< 0.05). In linear regression analysis, adiponectin levels had a significant association with IS and HDL-c (P= 0.03, P= 0.04) but an inverse relationship with IR, BMI, WC (B=-2.91, P= 0.04), and AIP (P< 0.05).

Conclusion

Increased leptin levels are related to high IR, AIP, and BMI among T2DM female patients. Similarly, adiponectin levels decrease IS and HDL-c. Therefore, obese T2DM women with high leptin and low adiponectin levels should be periodically checked to avoid or decrease consequences like CVD.

Distinct Associations of BMI and Fatty Acids With DNA Methylation in Fasting and Postprandial States in Men

We have previously shown that blood global DNA methylation (DNAm) differs between postprandial state (PS) and fasting state (FS) and is associated with BMI and polyunsaturated fatty acid (PUFA) (negatively and positively, respectively) in 12 metabolically healthy adult Mexican men (AMM cohort) equally distributed among conventional BMI classes. Here, we detailed those associations at CpG dinucleotide level by exploiting the Infinium methylation EPIC array (Illumina). We sought differentially methylated CpG (dmCpG) that were (1) associated with BMI (BMI-dmCpG) and/or fatty acids (FA) (FA-dmCpG) in FS or PS and (2) different across FS and PS within a BMI class. BMI-dmCpG and FA-dmCpG were more numerous in FS compared to PS and largely prandial state-specific. For saturated and monounsaturated FA, dmCpG overlap was higher across than within the respective saturation group. Several BMI- and FA-dmCpG mapped to genes involved in metabolic disease and in some cases matched published experimental data sets. Notably, SETDB1 and MTHFS promoter dmCpG could explain the previously observed associations between global DNAm, PUFA content, and BMI in FS. Surprisingly, overlap between BMI-dmCpG and FA-dmCpG was limited and the respective dmCpG were differentially distributed across functional genomic elements. BMI-dmCpG showed the highest overlap with dmCpG of the saturated FA palmitate, monounsaturated C20:1 and PUFA C20:2. Of these, selected promoter BMI-dmCpG showed opposite associations with palmitate compared to C20:1 and C20:2. As for the comparison between FS and PS within BMI classes, dmCpG were strikingly more abundant and variably methylated in overweight relative to normoweight or obese subjects (∼70–139-fold, respectively). Overweight-associated dmCpG-hosting genes were significantly enriched in targets for E47, SREBP1, and RREB1 transcription factors, which are known players in obesity and lipid homeostasis, but none overlapped with BMI-dmCpG. We show for the first time that the association of BMI and FA with methylation of disease-related genes is distinct in FS and PS and that limited overlap exists between BMI- and FA-dmCpG within and across prandial states. Our study also identifies a transcriptional regulation circuitry in overweight that might contribute to adaptation to that condition or to transition to obesity. Further work is necessary to define the pathophysiological implications of these findings.

Adiponectin-Consideration for its Role in Skeletal Muscle Health

Adiponectin regulates metabolism through blood glucose control and fatty acid oxidation, partly mediated by downstream effects of adiponectin signaling in skeletal muscle. More recently, skeletal muscle has been identified as a source of adiponectin expression, fueling interest in the role of adiponectin as both a circulating adipokine and a locally expressed paracrine/autocrine factor. In addition to being metabolically responsive, skeletal muscle functional capacity, calcium handling, growth and maintenance, regenerative capacity, and susceptibility to chronic inflammation are all strongly influenced by adiponectin stimulation. Furthermore, physical exercise has clear links to adiponectin expression and circulating concentrations in healthy and diseased populations. Greater physical activity is generally related to higher adiponectin expression while lower adiponectin levels are found in inactive obese, pre-diabetic, and diabetic populations. Exercise training typically restores plasma adiponectin and is associated with improved insulin sensitivity. Thus, the role of adiponectin signaling in skeletal muscle has expanded beyond that of a metabolic regulator to include several aspects of skeletal muscle function and maintenance critical to muscle health, many of which are responsive to, and mediated by, physical exercise.

Effect of diabetes on collagen metabolism and hypoxia in human gingival tissue: a stereological, histopathological, and immunohistochemical study

Diabetes mellitus and periodontitis are chronic inflammatory diseases that disrupt soft tissue metabolism. The diseases separately or together increase apoptosis in gingival fibroblast cells and reduce cell renewal. We investigated the effects of diabetes and periodontitis on the composition and structure of gingival connective tissue. We used gingival biopsies from 16 healthy individuals (control group, C), 16 type 2 diabetic patients with chronic periodontitis (diabetes + periodontitis group, D + P) and 16 healthy chronic periodontitis patients (periodontitis group, P). Biopsies were obtained under local anesthesia. Clinical attachment level (CAL), gingival index (GI) and plaque index (PI) were measured prior to gingival biopsies. Fibroblast cells were counted stereologically. Inflammatory cells were counted histomorphometrically. Hypoxia-inducible factor (HIF)-1α, lysyl hydroxylase (PLOD-2), neutrophil collagenase (MMP-8), and vascular endothelial growth factor (VEGF) levels were evaluated immunohistochemically. CAL, GI and PI for the C group were lower than for the other groups (p < 0.05). Fibroblast cell counts were lower for the D + P group than for the other groups (p < 0.05). Diabetes increased inflammatory cell numbers in the D and D + P groups compared to the C and P groups. MMP-8 levels were higher for the D + P group than for the other groups. VEGF was elevated in both the P and D + P groups compared to the C group, while HIF-1α and PLOD-2 levels were comparable. Diabetes increased tissue destruction and inflammation, and decreased fibroblast cell numbers without affecting collagen crosslinking and HIF-1α levels.

Lysyl hydroxylases are transcription targets for GATA3 driving lung cancer cell metastasis

Metastasis associates with late stages of lung cancer progression and remains the main cause of patient death due to the lack of clinically effective therapeutics. Here we report that the transcription factor GATA3 and its co-factor FOG2 commonly promote the expression of the lysyl hydroxylase (LH) family members, including LH2 and LH3, which in turn drive lung adenocarcinoma cell migration, invasion, and metastasis. We show evidence that both LH2 and LH3 are direct transcription targets for GATA3. Knockdown of either LH2 or LH3 suppresses migration and invasion; on the contrary, forced expression of LH2 or LH3 promotes growth and migration, suggesting that the two LHs exert redundant oncogenic functions. Importantly, re-expression of LH2 is sufficient to restore the metastatic capacity of GATA3-depleted cells, suggesting a role for LHs as the downstream mediators of GATA3. Collectively, our data reveal a pro-metastatic GATA3-LHs axis for lung cancer, supporting the notion that targeting LHs may be useful for treating lung cancer.

Collagen beta (1-O) galactosyltransferase 1 (GLT25D1) is required for the secretion of high molecular weight adiponectin and affects lipid accumulation

Secretion of high molecular weight (HMW) adiponectin is dependent on post-translational modification (PTM) of conserved lysines in the collagenous domain. The present study aims to characterize the enzymes responsible for the PTM of conserved lysines which leads to HMW adiponectin secretion, and to define its significance in relation to obesity. Collagen beta (1-O) galactosyltransferase 1 (GLT25D1) was knocked down in HEK cells modified for the stable expression of adiponectin (adiponectin expressing human embryonic kidney cells, Adipo-HEK) as well as in Simpson Golabi-Behmel-Syndrome (SGBS) adipocytes. Knockdown of GLT25D1 caused a significant decrease in HMW adiponectin in Adipo-HEK cells with no change in total adiponectin. Knockdown in the SGBS cells caused an increase in lipid accumulation yet inhibited adipogenesis. Co-immunoprecipitation with adiponectin and mass spectrometry showed that adiponectin formed a protein complex with lysyl hydroxylase 3 (LH3) and GLT25D1. Transient overexpression of GLT25D1 showed that the intracellular retention of LH3 was dependent on GLT25D1. To determine whether changes in GLT25D1 were significant in obesity, mice were fed a standard chow or high-fat diet (HFD) for 5 weeks. GLT25D1 was significantly decreased in mice fed HFD which coincided with a decrease in HMW adiponectin. We conclude that GLT25D1 regulates HMW adiponectin secretion and lipid accumulation, consistent with changes in mice after high-fat feeding. These results suggest a novel function of GLT25D1 leading to decreased HMW adiponectin secretion in early obesity.

C-reactive protein inhibits high-molecular-weight adiponectin expression in 3T3-L1 adipocytes via PI3K/Akt pathway

Adiponectin, an adipose-specific protein hormone, is secreted from white adipose tissue and involved in glucose and lipid metabolism. It is assembled into low-molecular-weight trimer (LMW), middle-molecular-weight hexameric (MMW) and high-molecular-weight (HMW), among which HMW exhibits higher activity. In this study, we proved that C-reactive protein (CRP), an inflammatory marker, inhibited adiponectin expression, especially HMW in time-and dose-dependent manners. Furthermore, CRP decreased the HMW/total adiponectin ration and reduced adiponectin assembly by increasing ERp44, and decreasing Ero1-α and DsbA-L. CRP activated pAkt, the downstream of PI3K. Inhibition of PI3K or pAkt abolished the effect of CRP. Our study suggested that CRP decreased adiponectin expression and multimerization, while CRP-induced decline in adiponectin might be mediated through the PI3K/Akt pathway.

[Adiponectin in health and disease]

Over the past 20 years after the discovery of adiponectin, much knowledge about its effect in health and disease has been gained. Adiponectin has antidiabetic, antiatherogenic, anti-inflammatory, immunomodulatory, metabolic, vasoprotective, and antiapoptotic properties. However, an understanding stems from the given literature review that much remains to be explored. Adiponectin has not yet commonly used in clinical practice, but cardiologists, endocrinologists, pediatricians, oncologists, and physicians of many specialties are interested in its preventive and therapeutic applications.

Electroacupuncture inhibits weight gain in diet-induced obese rats by activating hypothalamic LKB1-AMPK signaling

Background

Electroacupuncture (EA) is reported to be an effective treatment for obesity, but its mechanism is unclear. This study aimed to investigate the relationship between hypothalamic LKB1-AMPK-ACC signaling and EA.

Methods

Fifty male Sprague–Dawley rats were divided into two groups fed either chow (chow-fed group) or high-fat diet (HF group). After 4 weeks of feeding, obese rats in the HF group (defined as weighing 20 % or more than rats in the chow-fed group) were randomly allocated into an EA or Diet-induced obesity (DIO) group. The EA group was given EA on bilateral ST25–ST36 for 4 weeks, while the DIO group received no further intervention. Body weight of the chow-fed, DIO, and EA groups were measured weekly. mRNA and protein levels of the hypothalamic LKB1-AMPK-ACC signaling pathway were detected using real-time (RT)-PCR and western blot, respectively.

Results

After 4 weeks of EA treatment, the weight growth trend of rats in the EA group was inhibited compared with those in the DIO group. RT-PCR and western blotting showed that EA upregulated the transcription of Adenosine 5′-monophosphate -activated protein kinase α2 (AMPKα2), promoted protein expression of Liver kinase B1 (LKB1) and AMPKα1, and inhibited acetyl-CoA carboxylase (ACC) protein expression in the hypothalamus.

Conclusions

This study suggests that hypothalamic LKB1-AMPK-ACC signaling plays an important role in EA treatment for obesity.

Deficient copper concentrations in dried-defatted hepatic tissue from ob/ob mice: A potential model for study of defective copper regulation in metabolic liver disease

Ob/ob mice provide an animal model for non-alcoholic fatty liver disease/non-alcoholic steatohepatitis (NAFLD/NASH) in patients with obesity and type-2 diabetes. Low liver copper has been linked to hepatic lipid build-up (steatosis) in animals with systemic copper deficiency caused by low-copper diets. However, hepatic copper status in patients with NAFLD or NASH is uncertain, and a validated animal model useful for the study of hepatic copper regulation in common forms of metabolic liver disease is lacking. Here, we report parallel measurements of essential metal levels in whole-liver tissue and defatted-dried liver tissue from ob/ob and non-obese control mice. Measurements in whole-liver tissue from ob/ob mice at an age when they have developed NAFLD/NASH, provide compelling evidence for factitious lowering of copper and all other essential metals by steatosis, and so cannot be used to study hepatic metal regulation in this model. By marked contrast, metal measurements in defatted-dried liver samples reveal that most essential metals were actually normal and indicate specific lowering of copper in ob/ob mice, consistent with hepatic copper deficiency. Thus ob/ob mice can provide a model useful for the study of copper regulation in NAFLD and NASH, provided levels are measured in defatted-dried liver tissue.

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Ob/ob mice develop hepatic copper deficiency.

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Copper deficiency develops alongside NAFLD/NASH.

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Metal measurements in whole tissue are impacted by infiltrating fat.

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Levels of all essential metals are lower in ob/ob mice when measured in whole liver.

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After fat extraction, metal levels are normal, with the exception of copper.