Adipokines: inflammation and the pleiotropic role of white adipose tissue

I had been working on the endocrine and signalling role of white adipose tissue (WAT) since 1994 following the identification of the ob (Lep) gene(1), this after some 15 years investigating the physiological role of brown adipose tissue. The ob gene, a mutation in which it is responsible for the profound obesity of ob/ob (Lepob/Lepob) mice, is expressed primarily in white adipocytes and encodes the pleiotropic hormone leptin. The discovery of this adipocyte hormone had wide-ranging implications, including that white fat has multiple functions that far transcend the traditional picture of a simple lipid storage organ.

The transcription factor hepatocyte nuclear factor 4A acts in the intestine to promote white adipose tissue energy storage

The transcription factor hepatocyte nuclear factor 4 A (HNF4A) controls the metabolic features of several endodermal epithelia. Both HNF4A and HNF4G are redundant in the intestine and it remains unclear whether HNF4A alone controls intestinal lipid metabolism. Here we show that intestinal HNF4A is not required for intestinal lipid metabolism per se, but unexpectedly influences whole-body energy expenditure in diet-induced obesity (DIO). Deletion of intestinal HNF4A caused mice to become DIO-resistant with a preference for fat as an energy substrate and energetic changes in association with white adipose tissue (WAT) beiging. Intestinal HNF4A is crucial for the fat-induced release of glucose-dependent insulinotropic polypeptide (GIP), while the reintroduction of a stabilized GIP analog rescues the DIO resistance phenotype of the mutant mice. Our study provides evidence that intestinal HNF4A plays a non-redundant role in whole-body lipid homeostasis and points to a non-cell-autonomous regulatory circuit for body-fat management.

Edible red seaweed Campylaephora hypnaeoides J. Agardh alleviates obesity and related metabolic disorders in mice by suppressing oxidative stress and inflammatory response

Background The obesity epidemic has become a serious public health problem in many countries worldwide. Seaweed has few calories and is rich in active nutritional components necessary for health promotion and disease prevention. The aim of this study was to investigate the effects of the Campylaephora hypnaeoides J. Agardh (C. hypnaeoides), an edible seaweed traditionally eaten in Japan, on high-fat (HF) diet-induced obesity and related metabolic diseases in mice. Methods Male C57BL/6J mice were randomly divided into the following groups: normal diet group, HF diet group, HF diet supplemented with 2% C. hypnaeoides, and HF diet supplemented with 6% C. hypnaeoides. After 13 weeks of treatment, the weight of the white adipose tissue and liver, and the serum levels of glucose, insulin, adipokines, and lipids were measured. Hepatic levels of adipokines, oxidant markers, and antioxidant markers were also determined. Insulin resistance was assessed by a glucose tolerance test. Polysaccharides of C. hypnaeoides were purified and their molecular weight was determined by high-performance seize exclusion chromatography. The anti-inflammatory effects of purified polysaccharides were evaluated in RAW264.7 cells. Results Treatment of HF diet-induced obese mice with C. hypnaeoides for 13 weeks suppressed the increase in body weight and white adipose tissue weight. It also ameliorated insulin resistance, hyperglycemia, hepatic steatosis, and hypercholesterolemia. The ingestion of an HF diet increased serum levels of malondialdehyde (MDA), tumor necrosis factor α (TNF-α), and monocyte chemoattractant protein-1 (MCP-1), while it decreased serum adiponectin levels. In the liver, an HF diet markedly increased the MDA, TNF-α, and interleukin-6 (IL-6) levels, while it decreased glutathione and superoxide dismutase. These metabolic changes induced by HF diet feeding were ameliorated by dietary C. hypnaeoides. Purified polysaccharides and ethanol extract from C. hypnaeoides inhibited the lipopolysaccharide-induced overproduction of nitric oxide and TNF-α in macrophage RAW264.7 cells. Conclusions The present results indicated that C. hypnaeoides was able to alleviate HF diet-induced metabolic disorders, including obesity, hyperglycemia, hepatic steatosis, and hypercholesterolemia by attenuating inflammation and improving the antioxidant capacity in mice. Polysaccharides and polyphenols may be involved in these beneficial effects of C. hypnaeoides.

Effect of nutmeg extract on the white adipose tissue (WAT) browning process of aging rats

The white adipose tissue (WAT) browning process has become one of the promising methods for managing obesity. During this process, WAT is transformed into brown-like adipose tissue, which is also known as beige adipose tissue. The browning process can be activated by several inducers. One of the best candidates is peroxisome proliferator-activated receptor γ (PPARγ) agonist. Nutmeg (Myristica fragrans Houtt) is a natural PPARα/γ partial agonist that is known to contribute to the browning effect. This study aimed to explore the potential effect of nutmeg seed extract (NuSE) on body weight reduction and uncoupling protein (UCP)1, UCP2, UCP3, and peroxisome proliferator-activated receptor gamma coactivator-1 PGC-1α levels in aging rats. Eight male Wistar rats (80 weeks old) were divided into control and treatment groups. Both groups were fed a standard diet, and the treatment group was given 8.1 mg/kg body weight/day of NuSE via oral gavage for 12 weeks. After 12 weeks, the levels of UCP1, UCP2, UCP3, and PGC-1α from both inguinal WAT (iWAT) and interscapular brown adipose tissue (BAT) were examined. We observed that the administration of NuSE has no significant effect to the decreasement of rats body weights (p = 0.464), levels of UCP1 (p = 0.686), UCP2 (p = 0.360), UCP3 (p = 0.076), and PGC-1α (p = 0.200).

Beige Adipocyte As The Flame Of White Adipose Tissue: Regulation Of Browning And Impact Of Obesity

Beige adipocyte, the third and relatively new type of adipocyte, can emerge in white adipose tissue (WAT) under thermogenic stimulations that is termed as browning of WAT. Recent studies suggest that browning of WAT deserves more attention and therapies targeting browning of WAT can be helpful for reducing obesity. Beyond the major inducers of browning, namely cold and β3-adrenergic stimulation, beige adipocytes are affected by several factors, and excess adiposity per se may also influence the browning process. The objective of the present review is to provide an overview of recent clinical and preclinical studies on the hormonal and non-hormonal factors that affect the browning of WAT. This review further focuses on the role of obesity per se on browning process.

Effect of Exercise Training On Autophagic Process in White Adipose Tissue of High Fat Diet-Induced Obese Mice

Background. Some studies have established a relationship between obesity and the autophagic process in adipose tissue. This study aimed to investigate the effect of exercise training on the autophagic process in white adipose tissue (WAT) of high fat diet-induced obese mice.Methods and Results. C57BL/6 mice were assigned into three groups included: 1) Control 2), High-Fat Diet-induced Obesity (HFD-Ob), and 3) High-Fat Diet with Exercise Training (HFD-Ex). The subjects of HFD-Ob were fed a high-fat diet for 14 weeks. The mice of HFD-Ex had eight weeks of endurance training on a treadmill in addition to having the HFD. The Real-Time–PCR and western blot methods were used to measure the mRNA and protein levels of markers of the autophagic process. HFD caused an upregulation in the factors of the autophagosome formation, including ATG5 and ATG7, LC3, and the exercise training could augment the upregulation. Further, the training program prevented the change in LAMP2 expression (a marker of autophagolysosome), which being reduced by HFD. The lysosomal clearance factors (CTSB and CTSL) were raised in HFD-Ob and differently changed in HFD-Ex.Conclusion. HFD-induced obesity promoted the early and last steps of autophagy whereas defected the intermediate-step of it. Interestingly, the exercise training enhanced the early phase of autophagy, which being increased by HFD. Further, the training program could modify the rising effect of HFD on the last step of autophagy. It seems that a part of the protective effect of exercise training on obesity-related complications may be mediated by modulating the autophagic process in white adipose tissue.