Biology subjects

Spitler, K. M.

Publications and source records attributed to Spitler, K. M..

3 recordsLinked to original sources

bioRxiv2024

Sex-specific survival but not tissue wasting in the KPP mouse model of pancreatic cancer-induced cachexia

Cancer cachexia, a multifactorial condition resulting in muscle and adipose tissue wasting, reduces the quality of life of many people with cancer. Despite decades of research, therapeutic options for cancer cachexia remain limited. Cachexia is highly prevalent in people with pancreatic ductal adenocarcinoma (PDAC), and many animal models of pancreatic cancer are used to understand mechanisms underlying cachexia. One such model is the KrasLSL-G12D, Ptf1aCre-ER/+, Ptenflox/flox (KPP) model, which utilizes an inducible Cre recombinase to allow tumor development to be initiated at any age by tamoxifen administration. In our previous work, tumors were induced in KPP mice at 4 weeks of age. However, mice are still rapidly growing at this age, and a portion of the body weight differences seen between control and KPP mice is likely due to slowed growth of KPP mice. In our current study, pancreatic tumors were induced to develop with tamoxifen in KPP mice after rapid postnatal growth has slowed at 10 weeks of age (KPP10). Similar to our previous findings, KPP10 mice had lower body, muscle, and adipose tissue weights compared to non-tumor mice, and these differences were similar between male and female mice. However, male mice experienced greater relative weight loss. Unexpectedly, we identified that overall survival was significantly shorter in female KPP10 mice compared to KPP10 males. Greater body weight at tumor induction was associated with longer survival, suggesting that the sex difference in survival may be related to differences in body weight between male and female mice. NEW & NOTEWORTHY- Although male mice experience greater relative body weight losses, similar skeletal muscle and adipose tissue wasting occurs between male and female mice in the KrasLSL-G12D, Ptf1aCre-ER/+, Ptenflox/flox (KPP) model of pancreatic-cancer induced cachexia. - Greater weight loss in males may be related to longer survival. However, differences in tamoxifen dose relative to body weight may have accelerated tumor formation in female mice and therefore may be a relevant consideration for inducible tumor models.

physiology↗

bioRxiv2024

Effects of Age and Diet on Triglyceride Metabolism in Mice

BackgroundBoth age and diet can contribute to alterations in triglyceride metabolism and subsequent metabolic disease. In humans, plasma triglyceride levels increase with age. Diets high in saturated fats can increase triglyceride levels while diets high in omega-3 fatty acids decrease triglyceride levels. Here we asked how age and long-term diet effected triglyceride metabolism in mice. MethodsWe fed male and female mice a low-fat diet, a western diet, or a diet high in polyunsaturated and omega-3 (n-3) fatty acids for up to 2 years. We measured survival, body composition, plasma triglyceride levels, chylomicron clearance, and oral fat, glucose, and insulin tolerance. ResultsTriglyceride levels in mice did not increase with age, regardless of diet. Oral fat tolerance increased with age, while chylomicron clearance remained unchanged. Mice fed western diet had decreased survival. Interestingly, mice fed the n-3 diet gained more lean mass, and had lower insulin levels than mice fed either low-fat or western diet. Moreover, triglyceride uptake into the hearts of mice fed the n-3 diet was strikingly higher than in other groups. ConclusionsIn mice, age-induced changes in triglyceride metabolism did not match those in humans. Our data suggested that mice, like humans, had decreased fat absorption with age, but plasma triglyceride clearance did not decrease with age in mice, resulting in lower plasma triglyceride levels and improved oral fat tolerance with age. A chronic diet high in n-3 fatty acids increased insulin sensitivity and uptake of triglycerides specifically into the heart but how these observations are connected is unclear. Research PerspectivesO_LIThe changes in triglyceride metabolism that occur with age in humans are not reflected in a mouse model, thus mice are likely not an ideal model for understanding how age impacts lipid metabolism and subsequent metabolic disease. C_LIO_LIA fish-oil based high-fat diet high in omega-3 fatty acids significantly increases fatty acid uptake in the heart while at the same time decreases fasting insulin levels. C_LIO_LIIn future studies it will be important to understand how the omega-3 fatty acid induced increase in fatty acid uptake affects cardiac function and how it is related to other phenotypes induced by omega-3 fatty acids. C_LI

physiology↗

bioRxiv2020

ANGPTL4 from adipose, but not liver, is responsible for regulating plasma triglyceride partitioning

Elevated plasma triglyceride levels are associated with metabolic disease. Angiopoietin-like protein 4 (ANGPTL4) regulates plasma triglyceride levels by inhibiting lipoprotein lipase (LPL). Our aim was to investigate the role of tissue-specific ANGPTL4 expression in the setting of high fat diet. Adipocyte- and hepatocyte-specific ANGPTL4 deficient mice were fed a high fat diet (60% kCal from fat) for either 12 weeks or 6 months. We performed plasma metabolic measurements, triglyceride clearance and uptake assays, LPL activity assays, and assessed glucose homeostasis. Mice lacking adipocyte ANGPTL4 recapitulated the triglyceride phenotypes of whole-body ANGPTL4 deficiency, whereas mice lacking hepatocyte ANGPTL4 had few triglyceride phenotypes. When fed a high fat diet (HFD), mice deficient in adipocyte ANGPTL4 gained more weight, had enhanced adipose LPL activity, and initially had improved glucose and insulin sensitivity. However, this improvement was largely lost after 6 months on HFD. Conversely, mice deficient in hepatocyte ANGPTL4 initially displayed no differences in glucose homeostasis, but began to manifest improved glucose tolerance after 6 months on HFD. We conclude that it is primarily adipocyte-derived ANGPTL4 that is responsible for regulating plasma triglyceride levels. Deficiency in adipocyte- or hepatocyte-derived ANGPTL4 may confer some protections against high fat diet induced dysregulation of glucose homeostasis.

physiology↗