Type 2 diabetes is linked to higher physiologic markers of effort during exercise.

Background: People with type 2 diabetes (T2D) have lower rates of physical activity (PA) than the general population. This is significant because insufficient PA is linked to cardiovascular morbidity and mortality, particularly in individuals with T2D. Previously, we identified a novel barrier to physical activity: greater perceived effort during exercise in women. Specifically, women with T2D experienced exercise at low-intensity as greater effort than women without T2D at the same low-intensity - based on self-report and objective lactate measurements. A gap in the literature is whether T2D confers greater exercise effort in both sexes and across a range of work rates. Objectives: Our overarching objective was to address these gaps regarding the influence of T2D and relative work intensity on exercise effort. We hypothesized that T2D status would confer greater effort during exercise across a range of work rates below the aerobic threshold. Methods: This cross-sectional study enrolled males and post-menopausal females aged 50-75 years. Measures of exercise effort included: 1) heart rate, 2) lactate and 3) self-report of Rating of Perceived Exertion (RPE); each assessment was during the final minute of a 5-minute bout of treadmill exercise. Treadmill exercise was performed at 3 work rates: 1.5 mph, 2.0 mph, and 2.5 mph, respectively. To determine factors influencing effort, separate linear mixed effect models assessed the influence of T2D on each outcome of exercise effort, controlling for work rate intensity relative to peak oxygen consumption (%VO2peak). Models were adjusted for any significant demographic associations between effort and age (years), sex (male/female), baseline physical activity, or average blood glucose levels. Results: We enrolled n=19 people with T2D (47.4% female) and n=18 people (55.6% female) with no T2D. In the models adjusted for %VO2peak, T2D status was significantly associated with higher heart rate (p = 0.02) and lactate (p = 0.01), without a significant association with RPE (p = 0.58). Discussions: Across a range of low-to-moderate intensity work rates in older, sedentary males and females, a diagnosis of T2D conferred higher objective markers of effort but did not affect RPE. Greater objective effort cannot be fully attributed to impaired fitness, as it persisted despite adjustment for %VO2peak. In order to promote regular exercise and reduce cardiovascular risk for people with T2D, 1) further efforts to understand the mechanistic targets that influence physiologic exercise effort should be sought, and 2) comparison of the effort and tolerability of alternative exercise training prescriptions is warranted.

Effects of follicle-stimulating hormone on energy balance and tissue metabolic health after loss of ovarian function.

Loss of ovarian function imparts increased susceptibility to obesity and metabolic disease. These effects are largely attributed to decreased estradiol (E2), but the role of increased follicle-stimulating hormone (FSH) in modulating energy balance has not been fully investigated. Previous work that blocked FSH binding to its receptor in mice suggested this hormone may play a part in modulating body weight and energy expenditure after ovariectomy (OVX). We used an alternate approach to isolate the individual and combined contributions of FSH and E2 in mediating energy imbalance and changes in tissue-level metabolic health. Female Wistar rats were ovariectomized and given the gonadotropin releasing hormone (GnRH) antagonist degarelix to suppress FSH production. E2 and FSH were then added back individually and in combination for a period of 3 wk. Energy balance, body mass composition, and transcriptomic profiles of individual tissues were obtained. In contrast to previous studies, suppression and replacement of FSH in our paradigm had no effect on body weight, body composition, food intake, or energy expenditure. We did, however, observe organ-specific effects of FSH that produced unique transcriptomic signatures of FSH in retroperitoneal white adipose tissue. These included reductions in biological processes related to lipogenesis and carbohydrate transport. In addition, rats administered FSH had reduced liver triglyceride concentration (P < 0.001), which correlated with FSH-induced changes at the transcriptomic level. Although not appearing to modulate energy balance after loss of ovarian function in rats, FSH may still impart tissue-specific effects in the liver and white adipose tissue that might affect the metabolic health of those organs.NEW & NOTEWORTHY We find no effect of follicle-stimulating hormone (FSH) on energy balance using a novel model in which rats are ovariectomized, subjected to gonadotropin-releasing hormone antagonism, and systematically given back FSH by osmotic pump. However, tissue-specific effects of FSH on adipose tissue and liver were observed in this study. These include unique transcriptomic signatures induced by the hormone and a stark reduction in hepatic triglyceride accumulation.

Diabetes mellitus in breast cancer survivors: metabolic effects of endocrine therapy.

Breast cancer is the most common invasive malignancy in the world, with millions of survivors living today. Type 2 diabetes mellitus (T2DM) is also a globally prevalent disease that is a widely studied risk factor for breast cancer. Most breast tumours express the oestrogen receptor and are treated with systemic therapies designed to disrupt oestrogen-dependent signalling. Since the advent of targeted endocrine therapy six decades ago, the mortality from breast cancer has steadily declined; however, during the past decade, an elevated risk of T2DM after breast cancer treatment has been reported, particularly for those who received endocrine therapy. In this Review, we highlight key events in the history of endocrine therapies, beginning with the development of tamoxifen. We also summarize the sequence of reported adverse metabolic effects, which include dyslipidaemia, hepatic steatosis and impaired glucose tolerance. We discuss the limitations of determining a causal role for breast cancer treatments in T2DM development from epidemiological data and describe informative preclinical studies that suggest complex mechanisms through which endocrine therapy might drive T2DM risk and progression. We also reinforce the life-saving benefits of endocrine therapy and highlight the need for better predictive biomarkers of T2DM risk and preventive strategies for the growing population of breast cancer survivors.