Diet-induced obesity, energy metabolism and gut microbiota in C57BL/6J mice fed Western diets based on lean seafood or lean meat mixtures.

High protein diets may protect against diet-induced obesity, but little is known regarding the effects of different protein sources consumed at standard levels. We investigated how a mixture of lean seafood or lean meat in a Western background diet modulated diet-induced obesity, energy metabolism and gut microbiota. Male C57BL/6J mice fed a Western diet (WD) containing a mixture of lean seafood (seafood WD) for 12weeks accumulated less fat mass than mice fed a WD containing a mixture of lean meat (meat WD). Meat WD-fed mice exhibited increased fasting blood glucose, impaired glucose clearance, elevated fasting plasma insulin and increased plasma and liver lipid levels. We observed no first choice preference for either of the WDs, but over time, mice fed the seafood WD consumed less energy than mice fed the meat WD. Mice fed the seafood WD exhibited higher spontaneous locomotor activity and a lower respiratory exchange ratio (RER) than mice fed the meat WD. Thus, higher activity together with the decreased energy intake contributed to the different phenotypes observed in mice fed the seafood WD compared to mice fed the meat WD. Comparison of the gut microbiomes of mice fed the two WDs revealed significant differences in the relative abundance of operational taxonomic units (OTUs) belonging to the orders Bacteroidales and Clostridiales, with genes involved in metabolism of aromatic amino acids exhibiting higher relative abundance in the microbiomes of mice fed the seafood WD.

Tissue Inhibitor Of Matrix Metalloproteinase-1 Is Required for High-Fat Diet-Induced Glucose Intolerance and Hepatic Steatosis in Mice.

BACKGROUND: Plasma levels of tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) are elevated in obesity and obesity-related disorders, such as steatosis, but the metabolic role of TIMP-1 is unclear. Here we investigated how the presence or absence of TIMP-1 affected the development of diet-induced glucose intolerance and hepatic steatosis using the Timp1 null mice. METHODS: Timp1 knockout (TKO) and wild type (TWT) mice were fed chow, high-fat diet (HFD) or intermediate fat and sucrose diet (IFSD). We determined body weight, body composition, lipid content of the liver, energy intake, energy expenditure, oral glucose tolerance, as well as insulin tolerance. In addition, the histology of liver and adipose tissues was examined and expression of selected genes involved in lipid metabolism and inflammation in liver and adipose tissues was determined by RT-qPCR. RESULTS: TKO mice gained less weight and had lower energy efficiency than TWT mice when fed HFD, but not when fed chow or IFSD. Importantly, TKO mice were protected from development of HFD- as well as IFSD-induced glucose intolerance, hepatic steatosis, and altered expression of genes involved in hepatic lipid metabolism and inflammation. CONCLUSION: Collectively, our results indicate that TIMP-1 contributes to the development of diet-induced hepatic steatosis and glucose intolerance and may be a potential therapeutic target.

A mixture of cod and scallop protein reduces adiposity and improves glucose tolerance in high-fat fed male C57BL/6J mice.

Low-protein and high-protein diets regulate energy metabolism in animals and humans. To evaluate whether different dietary protein sources modulate energy balance when ingested at average levels obesity-prone male C57BL/6J mice were pair-fed high-fat diets (67 energy percent fat, 18 energy percent sucrose and 15 energy percent protein) with either casein, chicken filet or a mixture of cod and scallop (1:1 on amino acid content) as protein sources. At equal energy intake, casein and cod/scallop fed mice had lower feed efficiency than chicken fed mice, which translated into reduced adipose tissue masses after seven weeks of feeding. Chicken fed mice had elevated hepatic triglyceride relative to casein and cod/scallop fed mice and elevated 4 h fasted plasma cholesterol concentrations compared to low-fat and casein fed mice. In casein fed mice the reduced adiposity was likely related to the observed three percent lower apparent fat digestibility compared to low-fat, chicken and cod/scallop fed mice. After six weeks of feeding an oral glucose tolerance test revealed that despite their lean phenotype, casein fed mice had reduced glucose tolerance compared to low-fat, chicken and cod/scallop fed mice. In a separate set of mice, effects on metabolism were evaluated by indirect calorimetry before onset of diet-induced obesity. Spontaneous locomotor activity decreased in casein and chicken fed mice when shifting from low-fat to high-fat diets, but cod/scallop feeding tended (P = 0.06) to attenuate this decrease. Moreover, at this shift, energy expenditure decreased in all groups, but was decreased to a greater extent in casein fed than in cod/scallop fed mice, indicating that protein sources regulated energy expenditure differently. In conclusion, protein from different sources modulates energy balance in C57BL/6J mice when given at normal levels. Ingestion of a cod/scallop-mixture prevented diet-induced obesity compared to intake of chicken filet and preserved glucose tolerance compared to casein intake.

Scallop protein with endogenous high taurine and glycine content prevents high-fat, high-sucrose-induced obesity and improves plasma lipid profile in male C57BL/6J mice.

High-protein diets induce alterations in metabolism that may prevent diet-induced obesity. However, little is known as to whether different protein sources consumed at normal levels may affect diet-induced obesity and associated co-morbidities. We fed obesity-prone male C57BL/6J mice high-fat, high-sucrose diets with protein sources of increasing endogenous taurine content, i.e., chicken, cod, crab and scallop, for 6 weeks. The energy intake was lower in crab and scallop-fed mice than in chicken and cod-fed mice, but only scallop-fed mice gained less body and fat mass. Liver mass was reduced in scallop-fed mice, but otherwise no changes in lean body mass were observed between the groups. Feed efficiency and apparent nitrogen digestibility were reduced in scallop-fed mice suggesting alterations in energy utilization and metabolism. Overnight fasted plasma triacylglyceride, non-esterified fatty acids, glycerol and hydroxy-butyrate levels were significantly reduced, indicating reduced lipid mobilization in scallop-fed mice. The plasma HDL-to-total-cholesterol ratio was higher, suggesting increased reverse cholesterol transport or cholesterol clearance in scallop-fed mice in both fasted and non-fasted states. Dietary intake of taurine and glycine correlated negatively with body mass gain and total fat mass, while intake of all other amino acids correlated positively. Furthermore taurine and glycine intake correlated positively with improved plasma lipid profile, i.e., lower levels of plasma lipids and higher HDL-to-total-cholesterol ratio. In conclusion, dietary scallop protein completely prevents high-fat, high-sucrose-induced obesity whilst maintaining lean body mass and improving the plasma lipid profile in male C57BL/6J mice.

Hydrolyzed casein reduces diet-induced obesity in male C57BL/6J mice.

The digestion rate of dietary protein is a regulating factor for postprandial metabolism both in humans and animal models. However, few data exist about the habitual consumption of proteins with different digestion rates with regard to the development of body mass and diet-induced obesity. Here, we used a factorial ANOVA design to investigate the effects of protein form (intact vs. hydrolyzed casein) and protein level (16 vs. 32 energy percent protein) on body mass gain and adiposity in obesity-prone male C57BL/6J mice fed Western diets with 35 energy percent fat. Mice fed the hydrolyzed casein diets had higher spontaneous locomotor activity than mice fed intact casein. During the light phase, mice fed hydrolyzed casein tended (P = 0.08) to have a lower respiratory exchange ratio, indicating lower utilization of carbohydrates as energy substrate relative to those fed intact casein. In further support of less carbohydrate oxidation, plasma concentrations of glucose and those of the glucose metabolite lactate were lower in fed mice that consumed the hydrolyzed compared with the intact casein diet. Concomitantly, the plasma insulin concentration was strongly reduced in fed mice given hydrolyzed casein relative to those given intact casein. The mice fed hydrolyzed casein had greater ex vivo inguinal white adipose tissue non-CO2 ß-oxidation capacity along with induced expression of genes involved in mitochondrial fatty acid oxidation and mitochondrial uncoupling. The physiological changes induced by hydrolyzed casein ingestion translated into decreased body and adipose tissue masses. We conclude that chronic consumption of extensively hydrolyzed casein reduces body mass gain and diet-induced obesity in male C57BL/6J mice.

Stability, accumulation and cytotoxicity of an albumin-cisplatin adduct.

The accumulation and cytotoxicity of a 10 µmol L⁻¹ equimolar human serum albumin-cisplatin adduct (HSA-Pt) was investigated in suspension Ehrlich Ascites Tumor Cells (EATC) and adherent Ehrlich Lettré Ascites Cells (Lettré). HSA-Pt did not induce apoptosis nor was it taken up by the cells to any significant amount within 24 h incubation. The accumulation and cytotoxicity of HSA-Pt was compared to 10 µmol L⁻¹ cisplatin for which a larger accumulation and cytotoxicity were observed in EATC compared to Lettré. The experiment was performed with cell medium exchange every fourth hour as HSA-Pt and cisplatin were not stable in RPMI-1640 with 10% serum. The stability was determined using size exclusion chromatography-inductively coupled plasma-mass spectrometry (SEC-ICP-MS) and after 4 h new platinum peaks were observed. These findings indicate that before conducting cell experiments, the stability of the compound in the cell medium should be investigated especially when long exposure times are applied. Furthermore, HSA-Pt was found to be stable in Hanks Balanced Saline Solution (HBSS) and in Phosphate Buffered Saline (PBS) at pH 5.3, 6.1 and 7.4. Thus, the shift in pH when HSA-cisplatin passes from blood (pH 7.4) to tumor tissue (pH 5-6) is not capable of releasing cisplatin from HSA.

Pinpointing differences in cisplatin-induced apoptosis in adherent and non-adherent cancer cells.

Platinum compounds are used in the treatment of cancer. We demonstrate that cisplatin-induced (10 µM) apoptosis (caspase-3 activity) is pronounced within 18 hours in non-adherent Ehrlich ascites tumour cells (EATC), whereas there is no increase in caspase-3 activity in the adherent Ehrlich Lettré ascites tumour cells (ELA). Loss of KCl and cell shrinkage are hallmarks in apoptosis and has been shown in EATC. However, we find no reduction in cell volume and only a minor loss of K(+) which is accompanied by net uptake of Na(+) following 18 hours cisplatin exposure in ELA. Glutathione and taurine have previously been demonstrated to protect cells from apoptosis. We find, however, that increase or decrease in the cellular content of glutathione and taurine has no effect on cisplatin-induced cell death in EATC and ELA. Nevertheless, knock-down of the taurine transporter TauT leads to a significant increase in apoptosis in ELA following cisplatin exposure. We find that cytosolic accumulation of cisplatin is similar in EATC and ELA. However, the nuclear accumulation and DNA-binding of cisplatin is significant lower in ELA compared to EATC. We suggest three putative reasons for the observed cisplatin insensitivity in the adherent tumor cells (ELA) compared to the non-adherent tumor cells (EATC): less nuclear cisplatin accumulation, increased TauT activity, and decreased anion and water loss.