Octreotide promotes weight loss via suppression of intestinal MTP and apoB48 expression in diet-induced obesity rats

Si-Ni-San reverses dietary fat absorption defects in a murine model of depression

Depression is often associated with fatigue/energy loss. However, we lack a detailed understanding of the factors explaining this association. In this study, we uncovered that depressed mice have a defect in fat absorption, resulting in weight loss and reduced circulating lipid levels. Si-Ni-San (SNS), a basic formula of traditional Chinese medicine (TCM) for the treatment of depression, was found to not only alleviate depression-like behaviors, but also reverse the weight loss and dietary fat absorption of depressed mice. We found that SNS improved body weight and circulating lipid levels of depressed mice by up-regulating proteins [such as FFA uptake protein (CD36), TAG synthesis proteins (GPAT3, MOGAT2, DGAT1 and DGAT2) and chylomicron packaging proteins (MTP and APOB)] in the fat absorption pathway. Furthermore, cell-based results conducted with LPS-stimulated mouse MODE-K and human Caco-2 cells support that SNS, as well as Sinensetin (SIN) and Nobiletin (NOB), the two active components of the formula, have a role in regulating lipid absorption. Mechanistic studies revealed that SNS reverses body weight and fat absorption defects of depressed mice in part through the NR1D1/BMAL1/DGAT2 axis. These findings advance our understanding of the crosstalk between depression and energy loss, highlight the importance of gut function in disease management, and provide a basis for the application of SNS in the clinical treatment of depression and related disorders.

Treadmill exercise training improves the high-fat diet-induced behavioral changes in the male rats

The purpose of this study was to investigate the effects of treadmill exercise training on obesity-induced behavioral changes in high-fat diet (HFD)-induced male rats. In this study, 40 male Sprague-Dawley rats were divided into 4 groups after they were weaned: Control (C), Exercise (E), Obese (O) and Obese + Exercise (O + E). For the obesity model % 60 high-fat diet were applied. After obesity was induced, rats were either moderate aerobic exercise (treadmill running) trained or left untrained. Different tasks to assess spatial learning and memory (Morris water maze test (MWMT)), depressive-like behavior (forced swimming test(FST), tail suspension test (TST) and anxiety-like behavior (light-dark test (LDT) and open field test (OFT)) were conducted. Exercise caused a significant reduction in duration of immobility in the O group in FST and the decrease in immobility in the O + E rats in TST. The O + E rats demonstrated a significant increase in the time spent in the light box as compared to the O group in the LDT. The O + E rats did not show any behavioral alterations as compared to all the other groups in the OFT. In the O + E group, there was a significant increase in the time spent in the target quadrant compared to the O group in the MWMT. Our results support that treadmill exercise could improve cognitive, depressive-like, anxiety-like behavioral changes in the HFD-induced obese rats.

Suppression of Insulin Secretion in the Treatment of Obesity: A Systematic Review and Meta-Analysis

OBJECTIVE

This proof-of-concept study aimed to evaluate the efficacy and safety of suppression of insulin secretion in the treatment of obesity.

METHODS

A search of PubMed, Embase, and Cochrane databases was performed to identify randomized controlled trials (up to January 1, 2020) that used drugs that directly suppress insulin secretion (diazoxide or octreotide) in the treatment of obesity. The extracted data were analyzed using random-effects meta-analysis.

RESULTS

A total of seven randomized controlled trials were included, with four using diazoxide and three using octreotide to suppress insulin secretion. Suppression of insulin secretion significantly reduced fasting insulin level (mean difference: -3.94 mIU/L; 95% CI: -7.40 to -0.47) but slightly increased fasting blood glucose level (mean difference: 0.48 mmol/L; 95% CI: 0.24 to 0.72). Following the suppression of insulin secretion, significant reductions in body weight (mean difference: -3.19 kg; 95% CI: -5.71 to -0.66), BMI (mean difference: -1.65 kg/m² ; 95% CI: -2.41 to -0.90), and fat mass (mean difference: -5.92 kg; 95% CI: -8.28 to -3.56) were observed compared with placebo in the pooled data. No significant difference in fat-free mass was observed (mean difference: 0.56 kg; 95% CI: -0.40 to 1.52).

CONCLUSIONS

Results suggest that suppression of insulin secretion may lead to reduced body weight and fat mass with slightly increased blood glucose in individuals with obesity.

Dietary sn-2 palmitic triacylglycerols reduced faecal lipids, calcium contents and altered lipid metabolism in Sprague-Dawley rats

In this study, the impact of dietary sn-2 palmitic triacylglycerol (sn-2 PTAG) on faecal lipids, calcium excretion and lipid metabolic alternation was investigated in Sprague-Dawley (SD) rats fed with high-fat diet containing either palm olein (PO, sn-2 palmitic acid (PA) of 14.8%), sn-2 PTAG50 (sn-2 PA of 56.4%) or sn-2 PTAG70 (sn-2 PA of 72.4%), respectively. After 4-week feeding period, SD rats fed with sn-2 PTAGs showed reduced faecal soap fatty acids, neutral lipid and calcium excretion compared to those of PO-fed rats, whereas a significant difference was only observed for the sn-2 PTAG70-fed rats (p < .05). Moreover, dietary sn-2 PTAG70 also showed a significant effect on decreasing serum triacylglycerol (TAG) level, reducing perirenal adipocyte size and regulating lipid metabolism in small intestine and perirenal adipose tissue of SD rats. Significantly increased mRNA levels of genes involved in intestinal lipid anabolism as well as lipid catabolism were both observed in the sn-2 PTAG70-fed rats (p < .05). Meanwhile, dietary sn-2 PTAG70 also significantly up-regulated lipolysis, mitochondrial fatty acid oxidation and thermogenesis-related gene and protein levels in perirenal adipose tissue, which might be correlated with the reduced perirenal adipocyte size. Taken together, our findings indicated that sn-2 PTAG70 may have some beneficial effects on intestinal lipid utilisation and lipid metabolic activity for energy supply in visceral adipose tissue.

Effects of octreotide on hepatic glycogenesis in rats with high fat diet‑induced obesity

Reduced hepatic glycogenesis is one of the most important causes of metabolic abnormalities in non‑alcoholic fatty liver disease. Octreotide, a somatostatin analogue, has been demonstrated to promote weight loss and improve metabolic disorders in mice with high fat diet (HFD)‑induced obesity. However, whether octreotide affects hepatic glycogenesis is unknown. The aim of the present study was to verify the effects of octreotide on hepatic glycogenesis in rats with HFD‑induced obesity. Male Sprague‑Dawley rats were fed a standard diet or a HFD for 24 weeks. Obese rats from the HFD group were further divided into a HFD‑control group and an octreotide‑administered group. Rats in the latter group were injected with octreotide for 8 days. Glucose and insulin tolerance tests were performed, and the area under the curve (AUC) was calculated. Following sacrifice, their body weights and lengths, fasting plasma glucose (FPG), fasting insulin (FINS), serum triglyceride (TG), total cholesterol (TC), free fatty acid (FFA), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were measured. In addition, Lee's index and the homeostatic model assessment index were calculated. Hepatic TG, FFA levels and glycogen content were first determined. Hepatic steatosis in the obese rats was assessed based on hematoxylin and eosin and Oil Red O staining. Human hepatoblastoma HepG2 cells were divided into a control group, a palmitate (PA)‑treated group and a PA + octreotide‑treated group. Establishment of the in vitro fatty liver model using HepG2 cells was confirmed by Oil Red O staining. The expression of phosphorylated Akt and glycogen synthase kinase 3β (GSK3β) was detected by western blotting, and glycogen synthase (GS) mRNA levels were detected by reverse transcription‑quantitative polymerase chain reaction. Compared with the control group, the body weight, Lee's index, AUC of the intraperitoneal glucose tolerance test and intraperitoneal insulin tolerance test, levels of FPG, FINS, TG, TC, FFA, ALT and AST, and HOMA index values were significantly increased in the obese rats. The body weight, levels of FPG and FINS, and the HOMA index were significantly reduced following octreotide treatment, whereas the decrease in Lee's index, the blood levels of ALT, AST, TC, TG and FFA, and the AUC did not reach statistical significance. Hepatic TG and FFA levels were significantly increased and hepatic glycogen content was significantly decreased in rats with HFD‑induced obesity when compared with those in the control group. Octreotide intervention restored these alterations. The expression levels of phosphorylated Akt and GSK3β protein expression, as well as GS mRNA levels in the HFD group were lower when compared with those in the control group, whereas octreotide treatment reversed these reductions. The in vitro experiments demonstrated that the reduced levels of phosphorylated Akt and GSK3β protein, and GS mRNA in the PA‑treated group were significantly reversed by octreotide treatment. In conclusion, the results indicate that octreotide improved hepatic glycogenesis and decreased FPG concentration in rats with HFD‑induced obesity. These mechanisms may be associated with increased GS activity via the promotion of GSK3β phosphorylation. Therefore, octreotide may be regarded as a novel therapeutic strategy for HFD‑induced obesity and obesity‑associated metabolic disorders.

Cardiomyocyte Regulation of Systemic Lipid Metabolism by the Apolipoprotein B-Containing Lipoproteins in Drosophila

The heart has emerged as an important organ in the regulation of systemic lipid homeostasis; however, the underlying mechanism remains poorly understood. Here, we show that Drosophila cardiomyocytes regulate systemic lipid metabolism by producing apolipoprotein B-containing lipoproteins (apoB-lipoproteins), essential lipid carriers that are so far known to be generated only in the fat body. In a Drosophila genetic screen, we discovered that when haplo-insufficient, microsomal triglyceride transfer protein (mtp), required for the biosynthesis of apoB-lipoproteins, suppressed the development of diet-induced obesity. Tissue-specific inhibition of Mtp revealed that whereas knockdown of mtp only in the fat body decreases systemic triglyceride (TG) content on normal food diet (NFD) as expected, knockdown of mtp only in the cardiomyocytes also equally decreases systemic TG content on NFD, suggesting that the cardiomyocyte- and fat body-derived apoB-lipoproteins serve similarly important roles in regulating whole-body lipid metabolism. Unexpectedly, on high fat diet (HFD), knockdown of mtp in the cardiomyocytes, but not in fat body, protects against the gain in systemic TG levels. We further showed that inhibition of the Drosophila apoB homologue, apolipophorin or apoLpp, another gene essential for apoB-lipoprotein biosynthesis, affects systemic TG levels similarly to that of Mtp inhibition in the cardiomyocytes on NFD or HFD. Finally, we determined that HFD differentially alters Mtp and apoLpp expression in the cardiomyocytes versus the fat body, culminating in higher Mtp and apoLpp levels in the cardiomyocytes than in fat body and possibly underlying the predominant role of cardiomyocyte-derived apoB-lipoproteins in lipid metabolic regulation. Our findings reveal a novel and significant function of heart-mediated apoB-lipoproteins in controlling lipid homeostasis.

The heart is increasingly recognized to serve an important role in the regulation of whole-body lipid homeostasis; however, the underlying mechanisms remained poorly understood. Here, our study in Drosophila reveals that cardiomyocytes regulate systemic lipid metabolism by producing apolipoprotein B-containing lipoproteins (apoB-lipoproteins), essential lipid carriers that are so far known to be generated only in the fat body (insect liver and adipose tissue). We found that apoB-lipoproteins generated by the Drosophila cardiomyocytes serve an equally significant role as their fat body-derived counterparts in maintaining systemic lipid homeostasis on normal food diet. Importantly, on high fat diet (HFD), the cardiomyocyte-derived apoB-lipoproteins are the major determinants of whole-body lipid metabolism, a role which could be attributed to the HFD-induced up-regulation of apoB-lipoprotein biosynthesis genes in the cardiomyocytes and their down-regulation in the fat body. Taken together, our results reveal that apoB-lipoproteins are new players in mediating the heart control of lipid metabolism, and provide first evidence supporting the notion that HFD-induced differential regulation of apoB-lipoprotein biosynthesis genes could alter the input of different tissue-derived apoB-lipoproteins in systemic lipid metabolic control.

Korean pine nut oil replacement decreases intestinal lipid uptake while improves hepatic lipid metabolism in mice

BACKGROUND/OBJECTIVES

Consumption of pine nut oil (PNO) was shown to reduce weight gain and attenuate hepatic steatosis in mice fed a high-fat diet (HFD). The aim of this study was to examine the effects of PNO on both intestinal and hepatic lipid metabolism in mice fed control or HFD.

MATERIALS/METHODS

Five-week-old C57BL/6 mice were fed control diets containing 10% energy fat from either Soybean Oil (SBO) or PNO, or HFD containing 15% energy fat from lard and 30% energy fat from SBO or PNO for 12 weeks. Expression of genes related to intestinal fatty acid (FA) uptake and channeling (Cd36, Fatp4, Acsl5, Acbp), intestinal chylomicron synthesis (Mtp, ApoB48, ApoA4), hepatic lipid uptake and channeling (Lrp1, Fatp5, Acsl1, Acbp), hepatic triacylglycerol (TAG) lipolysis and FA oxidation (Atgl, Cpt1a, Acadl, Ehhadh, Acaa1), as well as very low-density lipoprotein (VLDL) assembly (ApoB100) were determined by real-time PCR.

RESULTS

In intestine, significantly lower Cd36 mRNA expression (P < 0.05) and a tendency of lower ApoA4 mRNA levels (P = 0.07) was observed in PNO-fed mice, indicating that PNO consumption may decrease intestinal FA uptake and chylomicron assembly. PNO consumption tended to result in higher hepatic mRNA levels of Atgl (P = 0.08) and Cpt1a (P = 0.05). Significantly higher hepatic mRNA levels of Acadl and ApoB100 were detected in mice fed PNO diet (P < 0.05). These results suggest that PNO could increase hepatic TAG metabolism; mitochondrial fatty acid oxidation and VLDL assembly.

CONCLUSIONS

PNO replacement in the diet might function in prevention of excessive lipid uptake by intestine and improve hepatic lipid metabolism in both control diet and HFD fed mice.

Effect of Octreotide on Hepatic Steatosis in Diet-Induced Obesity in Rats

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) caused by liver lipid dysregulation is linked to obesity. Somatostatin (SST) and its analogs have been used to treat pediatric hypothalamic obesity. However, the application of such drugs for the treatment of NAFLD has not been evaluated.

OBJECTIVE

This study aimed to investigate the expression levels of important regulators of hepatic lipid metabolism and the possible effect of the SST analog octreotide on these regulators.

METHODS

SD rats were assigned to a control group and a high-fat diet group. Obese rats from the high-fat diet group were further divided into the obese and octreotide-treated groups. The body weight, plasma SST, fasting plasma glucose (FPG), insulin, triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and free fatty acid (FFA) levels were measured. Hepatic steatosis was evaluated based on the liver TG content, HE staining and oil red O staining. The SREBP-1c, ACC1, FAS, MTP, apoB and ADRP expression levels in the liver were also determined by RT-PCR, qRT-PCR, western blot or ELISA.

RESULTS

The obese rats induced by high-fat diet expressed more SREBP-1c, FAS and ADRP but less MTP protein in the liver than those of control rats, whereas octreotide intervention reversed these changes and increased the level of apoB protein. Compared to the control group, obese rats showed increased liver ACC1, SREBP-1c and apoB mRNA levels, whereas octreotide-treated rats showed decreased mRNA levels of apoB and SREBP-1c. This was accompanied by increased body weight, liver TG contents, FPG, TG, TC, LDL-C, FFA, insulin and derived homeostatic model assessment (HOMA) values. Octreotide intervention significantly decreased these parameters. Compared to the control group, the obese group showed a decreasing trend on plasma SST levels, which were significantly increased by the octreotide intervention.

CONCLUSION

Octreotide can ameliorate hepatic steatosis in obese rats, possibly by decreasing hepatic lipogenesis and increasing TG export from hepatocytes.

Cyclocarya paliurus prevents high fat diet induced hyperlipidemia and obesity in Sprague-Dawley rats

Cyclocarya paliurus (CP; qing qian liu), which is used as an herbal tea in China, has been confirmed to have therapeutic effects on hyperlipidemia and obesity, and therefore it is widely consumed to prevent metabolic diseases such as hyperlipidemia and diabetes. In this study, we investigated the preventive effects of CP on obesity and hyperlipidemia, as well as the underlying mechanisms involved in intestinal secretion of apolipoprotein (apo) B48. Sprague-Dawley rats were fed a high-fat diet (HFD) and with or without various concentrations of an ethanol extract of CP (CPE; 2, 4, or 8 g·(kg body mass)(-1)) administered by gavage for 8 weeks. From the results we see that CPE dose-dependently blocked increases in body mass, and decreased food utilization as well as visceral fat mass. Decreased serum levels of total cholesterol, triglycerides, and low density lipoprotein cholesterol, and elevated levels of high density lipoprotein cholesterol, as well as lowered levels of total cholesterol and triglycerides in the liver were also noticed in CPE-treated rats. Magnetic resonance images indicated that the abnormal fat storage induced by the HFD was obviously suppressed by CPE. In addition, ELISA analysis showed reduced fasting serum apoB48 in the CPE treatment groups. Based on the above results, CPE shows a promising preventive effect on obesity and hyperlipidemia, partially through suppressing intestinal apoB48 overproduction.

The gut sensor as regulator of body weight

The gastrointestinal (GI) tract comprises a large endocrine organ that regulates not only nutrient sensing and metabolising but also satiety and energy homeostasis. More than 20 hormones secreted from the stomach, intestine, and pancreas as well as signaling mediators of the gut microbiome are involved in this process. A better understanding of how related pathways affect body weight and food intake will help us to find new strategies and drugs to treat obesity. For example, weight loss secondary to lifestyle intervention is often accompanied by unfavorable changes in multiple GI hormones, which may cause difficulties in maintaining a lower body weight status. Conversely, bariatric surgery favorably changes the hormone profile to support improved satiety and metabolic function. This partially explains stronger sustained body weight reduction resulting in better long-term results of improved metabolic functions. This review focuses on GI hormones and signaling mediators of the microbiome involved in satiety regulation and energy homeostasis and summarizes their changes following weight loss. Furthermore, the potential role of GI hormones as anti-obesity drugs is discussed.