Visceral adiposity is associated with increased diabetes risk, while expansion of subcutaneous adipose tissue may be protective. However, the visceral compartment contains different fat depots. ...Peripancreatic adipose tissue (PAT) is an understudied visceral fat depot. Here, we aimed to define PAT functionality in lean and high-fat-diet (HFD)-induced obese mice.
Four adipose tissue depots (inguinal, mesenteric, gonadal, and peripancreatic adipose tissue) from chow- and HFD-fed male mice were compared with respect to adipocyte size (n = 4-5/group), cellular composition (FACS analysis, n = 5-6/group), lipogenesis and lipolysis (n = 3/group), and gene expression (n = 6-10/group). Radioactive tracers were used to compare lipid and glucose metabolism between these four fat depots in vivo (n = 5-11/group). To determine the role of PAT in obesity-associated metabolic disturbances, PAT was surgically removed prior to challenging the mice with HFD. PAT-ectomized mice were compared to sham controls with respect to glucose tolerance, basal and glucose-stimulated insulin levels, hepatic and pancreatic steatosis, and gene expression (n = 8-10/group).
We found that PAT is a tiny fat depot (~0.2% of the total fat mass) containing relatively small adipocytes and many "non-adipocytes" such as leukocytes and fibroblasts. PAT was distinguished from the other fat depots by increased glucose uptake and increased fatty acid oxidation in both lean and obese mice. Moreover, PAT was the only fat depot where the tissue weight correlated positively with liver weight in obese mice (R = 0.65; p = 0.009). Surgical removal of PAT followed by 16-week HFD feeding was associated with aggravated hepatic steatosis (p = 0.008) and higher basal (p < 0.05) and glucose-stimulated insulin levels (p < 0.01). PAT removal also led to enlarged pancreatic islets and increased pancreatic expression of markers of glucose-stimulated insulin secretion and islet development (p < 0.05).
PAT is a small metabolically highly active fat depot that plays a previously unrecognized role in the pathogenesis of hepatic steatosis and insulin resistance in advanced obesity.
Context: There is currently no consensus regarding optimal dose or dose-range of buprenorphine (BUP) for treatment of opioid use disorder (OUD).
Objective: To elucidate the relationship between BUP ...dose and opioid receptor blockade, retention in treatment and illicit opioid drug use.
Methods: Systematic review of the scientific literature through searches in the databases MEDLINE and PubMed.
Results: The review of the opioid receptor blockade studies did not find evidence that a daily sublingual (SL) BUP tablet dose higher than 16 mg confers added blockade benefit, while doses under 8 mg are insufficient to produce opioid receptor blockade. The data are inconclusive regarding the relative effectiveness of an 8 mg SL BUP tablet dose versus a 16 mg SL BUP tablet dose in terms of opioid receptor blockade. The review did not establish any clear relationship between BUP dose and treatment retention or illicit opioid use.
Conclusions: The BUP dose in treatment of OUD should be individualized based on a continuous clinical benefit-risk assessment. Further research is needed to better understand the relationship between dose and efficacy over time in patients with this complex disorder.
Aims: To characterise and understand the untreated high-risk opioid user population in Finland, and to determine the reasons why these people do not enter treatment. Methods: The study setting was a ...half-year cross-sectional survey in Finland during 2021–2022. An electronic questionnaire with 24 structured questions was concluded in 16 needle exchange units. Participants were opioid-dependent people without opioid agonist treatment (OAT), and they answered the survey voluntarily and anonymously. Results: Of the 167 respondents, 62% were men, 53% were aged ≤34 years, 66% had used opioids for >6 years, and 78% used drugs intravenously (IV) daily. The most used opioid (95%) was buprenorphine. Most respondents used opioids as self-medication for withdrawal symptoms (75%), or to treat psychological symptoms (59%) or pain (43%). Of them, 70% also used other substances for recreational purposes. The most common named reasons to stay outside OAT were as follows: seeking treatment is too difficult (37%); treatment is too binding (36%); and fear of actions from authorities (23%). Conclusions: For opioid-dependent respondents who would be eligible for OAT in Finland, treatment awareness is limited. These high-risk opioid users also think that the treatment would be too binding. In conclusion, there is a need for increase in general information about, accessibility to, acceptance for and individualisation of OAT.
Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) transports Ca2+ from the cytosol into the endoplasmic retitculum (ER) and is essential for appropriate regulation of intracellular Ca2+ homeostasis. ...The objective of this study was to test the hypothesis that SERCA pumps are involved in the regulation of white adipocyte hormone secretion and other aspects of adipose tissue function and that this control is disturbed in obesity-induced type-2 diabetes.
SERCA expression was measured in isolated human and mouse adipocytes as well as in whole mouse adipose tissue by Western blot and RT-qPCR. To test the significance of SERCA2 in adipocyte functionality and whole-body metabolism, we generated adipocyte-specific SERCA2 knockout mice. The mice were metabolically phenotyped by glucose tolerance and tracer studies, histological analyses, measurements of glucose-stimulated insulin release in isolated islets, and gene/protein expression analyses. We also tested the effect of pharmacological SERCA inhibition and genetic SERCA2 ablation in cultured adipocytes. Intracellular and mitochondrial Ca2+ levels were recorded with dual-wavelength ratio imaging and mitochondrial function was assessed by Seahorse technology.
We demonstrate that SERCA2 is downregulated in white adipocytes from patients with obesity and type-2 diabetes as well as in adipocytes from diet-induced obese mice. SERCA2-ablated adipocytes display disturbed Ca2+ homeostasis associated with upregulated ER stress markers and impaired hormone release. These adipocyte alterations are linked to mild lipodystrophy, reduced adiponectin levels, and impaired glucose tolerance. Interestingly, adipocyte-specific SERCA2 ablation leads to increased glucose uptake in white adipose tissue while the glucose uptake is reduced in brown adipose tissue. This dichotomous effect on glucose uptake is due to differently regulated mitochondrial function. In white adipocytes, SERCA2 deficiency triggers an adaptive increase in fibroblast growth factor 21 (FGF21), increased mitochondrial uncoupling protein 1 (UCP1) levels, and increased oxygen consumption rate (OCR). In contrast, brown SERCA2 null adipocytes display reduced OCR despite increased mitochondrial content and UCP1 levels compared to wild type controls.
Our data suggest causal links between reduced white adipocyte SERCA2 levels, deranged adipocyte Ca2+ homeostasis, adipose tissue dysfunction and type-2 diabetes.
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•Adipocyte SERCA2 is downregulated in human subjects with type-2 diabetes.•Loss of SERCA2 disturbs the intracellular Ca2+ homeostasis in adipocytes.•Impaired metabolism and altered adipokine levels in adipocyte-SERCA2 null mice.•Loss of SERCA2 accelerates metabolic processes in white adipocytes.•Loss of SERCA2 impairs the mitochondrial function of brown adipocytes.
Abstract Objective The bacteria Staphylococcus aureus is part of the normal bacterial flora and produces a repertoire of enterotoxins which can cause food poisoning and toxic shock and might ...contribute to the pathogenesis of inflammatory diseases. These enterotoxins directly cross-link the T cell receptor with MHC class II, activating large amounts of T cells and are therefore called superantigens. It was recently discovered that the superantigen SEA binds to the cytokine receptor gp130. As obesity and type 2 diabetes are highly associated with inflammation of the adipose tissue and gp130 has been shown to play an important role in adipocytes, we wanted to investigate the effect of SEA on adipocyte signaling and function. Materials/methods Binding of SEA to gp130 was examined using surface plasmon resonance in a cell free system. Effects of SEA on adipocyte signaling, insulin sensitivity and function were studied using western blotting and biological assays for lipolysis, lipogenesis and glucose uptake. Results We demonstrate that SEA binds to gp130 with a medium affinity. Furthermore, SEA induces phosphorylation of a key downstream target, STAT3, in adipocytes. SEA also inhibits insulin-induced activation of PKB and PKB downstream signaling which was associated with reduced basal and insulin induced glucose uptake, reduced lipogenesis as well as reduced ability of insulin to inhibit lipolysis. Conclusions SEA inhibits insulin signaling as well as insulin biological responses in adipocytes supporting that bacterial infection might contribute to the development of insulin resistance and type 2 diabetes.
•CARTtg mice display a normal metabolic phenotype under basal conditions.•After metabolic challenging CARTtg mice display increased insulin secretion.•After metabolic challenging CARTtg mice display ...improved glycemia.
Impaired beta cell function and beta cell death are key features of type 2 diabetes (T2D). Cocaine- and amphetamine-regulated transcript (CART) is necessary for normal islet function in mice. CART increases glucose-stimulated insulin secretion in vivo in mice and in vitro in human islets and CART protects beta cells against glucotoxicity-induced cell death in vitro in rats. Furthermore, beta cell CART is upregulated in T2D patients and in diabetic rodent models as a consequence of hyperglycaemia. The aim of this study was to assess the impact of upregulated beta cell CART on islet hormone secretion and glucose homeostasis in a transgenic mouse model.
To this end, mice with beta cell-specific overexpression of CART (CARTtg mice) were generated. CARTtg mice challenged by aging, high fat diet feeding or streptozotocin treatment were phenotyped with respect to in vivo and in vitro insulin and glucagon secretion, glucose homeostasis, and beta cell mass. In addition, the impact of adenoviral overexpression of CART on insulin secretion was studied in INS-1 832/13 cells.
CARTtg mice had a normal metabolic phenotype under basal conditions. On the other hand, with age CARTtg mice displayed increased insulin secretion and improved glucose elimination, compared with age-matched WT mice. Furthermore, compared with WT controls, CARTtg mice had increased insulin secretion after feeding a high fat diet, as well as lower glucose levels and higher insulin secretion after streptozotocin treatment. Viral overexpression of CART in INS-1 832/13 cells resulted in increased glucose-stimulated insulin secretion. Together, these results imply that beta cell CART acts to increase insulin secretion when beta cell function is challenged. We propose that the increase in beta cell CART is part of a compensatory mechanisms trying to counteract the hyperglycaemia in T2D.
Glucagon-like peptide 1 (GLP-1) and serotonin play critical roles in energy balance regulation. Both systems are exploited clinically as antiobesity strategies. Surprisingly, whether they interact in ...order to regulate energy balance is poorly understood. Here we investigated mechanisms by which GLP-1 and serotonin interact at the level of the central nervous system. Serotonin depletion impaired the ability of exendin-4, a clinically used GLP-1 analog, to reduce body weight in rats, suggesting that serotonin is a critical mediator of the energy balance impact of GLP-1 receptor (GLP-1R) activation. Serotonin turnover and expression of 5-hydroxytryptamine (5-HT) 2A (5-HT
) and 5-HT
serotonin receptors in the hypothalamus were altered by GLP-1R activation. We demonstrate that the 5-HT
, but surprisingly not the 5-HT
, receptor is critical for weight loss, anorexia, and fat mass reduction induced by central GLP-1R activation. Importantly, central 5-HT
receptors are also required for peripherally injected liraglutide to reduce feeding and weight. Dorsal raphe (DR) harbors cell bodies of serotonin-producing neurons that supply serotonin to the hypothalamic nuclei. We show that GLP-1R stimulation in DR is sufficient to induce hypophagia and increase the electrical activity of the DR serotonin neurons. Finally, our results disassociate brain metabolic and emotionality pathways impacted by GLP-1R activation. This study identifies serotonin as a new critical neural substrate for GLP-1 impact on energy homeostasis and expands the current map of brain areas impacted by GLP-1R activation.
Peripancreatic adipose tissue (PAT) is an understudied visceral fat depot that surrounds pancreas and is in touch with spleen and liver. Recent previous studies suggest that obesity-associated PAT ...inflammation accelerates pancreatic neoplasia in KrasG12D mice and that PAT conditioned-medium from pre-diabetic rats (9 weeks on high-fat diet; HFD) stimulates insulin secretion, proliferation and apoptosis in INS-1 cells. In this study, we aimed to better characterize PAT functionality in the context of HFD-induced obesity. PAT is a very small depot (0,5 ±0,04 mg) with a relatively high number of small adipocytes in unchallenged mice on chow, and we found that PAT expansion is less pronounced at early stages of HFD-feeding compared to the expansion of inguinal (IWAT), gonadal (GWAT) and mesenteric adipose tissues (MWAT). After 8-weeks HFD feeding the expansion of PAT was however comparable to the other three fat depots, but still PAT was more protected against the deleterious effects of HFD on adipose tissue inflammation and insulin resistance as judged by gene expression analysis (adiponectin, insulin receptor and inflammation markers). Feeding after 16-weeks HFD reduced the glucose and lipid uptake in all fat depots however, it was less pronounced in PAT; both fatty acid and glucose oxidation rates were higher in PAT compared to IWAT, GWAT and MWAT. Moreover, we noted that PAT is the only fat depot where the tissue weight correlates positively with liver weight in HFD-induced obese mice, and surgical removal of PAT followed by 16-week-HFD-feeding was associated with increased hepatic triglyceride content and accumulation of more and larger lipid droplets. PAT did not regenerate during this 16-week HFD time course suggesting that its precursor cells reside within the depot. Taken all data together, we propose that PAT, although it is located in the visceral compartment, can be considered as a metabolically/immunologically healthy fat depot that protects against hepatic steatosis in advanced obesity.
Disclosure
B. Chanclón: None. P. Micallef: None. E. Banke Nordbeck: None. Y. Wu: None. B. Wilder: None. J. Kanerva: None. P. Rorsman: None. I. Wernstedt Asterholm: None.
The white adipocyte hormone adiponectin is released in different molecular forms and a reduction of high-molecular weight (HMW) adiponectin has specifically been associated with the development of ...metabolic disease. We have recently shown that adiponectin is released via cAMP/epinephrine-stimulated exocytosis, involving activation of beta 3 adrenergic receptors (beta3ARs). However, a number of studies have, seemingly incompatible with the catecholamine-triggered release, reported that insulin (lowers cAMP) increases adiponectin secretion. Here we have pinpointed the differences between insulin- and catecholamine-stimulated short-term adiponectin secretion. Using a combination of biophysical and biochemical techniques applied to mouse and human adipocytes as well as whole animal studies, we show that catecholamines specifically stimulate the rapid exocytosis of high-molecular weight (HMW) adiponectin. In contrast, insulin induces secretion of smaller adiponectin forms only, with slower time kinetics. The catecholamine-stimulated secretion of HMW adiponectin is blunted in adipocytes isolated from obese and diabetic mice (8 weeks high-fat diet) and this secretory defect is paralleled by a ∼50% reduction of serum HMW adiponectin. The insulin-induced release of smaller adiponectin forms is also abrogated i adipocytes from obese/diabetic mice. However, the total serum adiponectin level remains unaltered, likely due to enhanced basal (unstimulated) release of smaller adiponectin forms. Our findings suggest that insulin and catecholamines have entirely different roles in the regulation of adiponectin secretion and demonstrate a previously unknown role of beta3ARs for human white adipocyte physiology. We propose that the reduced levels of HMW adiponectin observed in diabetic individuals, and that have been linked to the development of metabolic disease, is a result of a secretory disturbance largely depending on disrupted adrenergic signaling.
Disclosure
S. Musovic: None. A.M. Komai: None. E. Banke Nordbeck: None. U.A. Noor: None. I. Wernstedt Asterholm: None. C.S. Olofsson: None.
Funding
Swedish Diabetes Foundation; Knut and Alice Wallenberg Foundation; Swedish Medical Research Council
Obesity represents one of the most important health problems. Proper adipose tissue expandability is crucial for avoiding metabolic disorders. Furthermore, not all fat depots are functionally equal. ...Our previous work indicates that the expansion of the mesenteric adipose tissue (MWAT) plays a role in the intestinal barrier. Whether pancreas-associated adipose tissue (PAT) has a specific function is currently unknown. We hypothesize that storage of excess nutrients in PAT and PAT-derived adipokines (such as adiponectin) protect the pancreas against metabolic dysfunction during weight gain/obesity. An initial morphological study showed that PAT has an increased number of small, but fewer large adipocytes relative the adjacent MWAT. We compared the response to a 16-week high-fat diet (HFD)/obesity between PAT, other fat depots and pancreas. We found higher mRNA expression of inflammation markers in MWAT, inguinal (IWAT) and gonadal fat (GWAT), but not in PAT in response to HFD/obesity. HFD also downregulated the expression of insulin receptor and adiponectin in all fat depots, but not in PAT. The pancreas showed an increase in inflammatory and insulin resistance markers only after long-term (16 weeks) HFD exposure, a time point when also PAT displayed a reduction in insulin receptor and adiponectin expression. Smaller adipocytes are typically more functional than large adipocytes. Thus, these data suggest that PAT have an increased capacity for energy storage. This in turn may protect the pancreas against ectopic lipid accumulation and lipotoxicity. Moreover, our data show that PAT is protected against the deleterious effects of HFD, maintaining normal mRNA levels of adiponectin, insulin receptor and markers of inflammation.
In summary, we believe that PAT protects the pancreatic beta-cells from lipotoxicity through its increased capacity for energy storage, sustained insulin sensitivity and possibly also increased insulin exposure because of its anatomical location.
Disclosure
B. Chanclon Garcia: None. Y. Wu: None. E. Banke Nordbeck: None. S. Musovic: None. C.S. Olofsson: None. P. Rorsman: None. I. Wernstedt Asterholm: None.
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