Metrics of Diabetes Risk Are Only Minimally Improved by Exercise Training in Postmenopausal Breast Cancer Survivors

Physical Activity, Insulin Resistance and Cancer: A Systematic Review

INTRODUCTION

Insulin resistance (IR), a key aspect of type 2 diabetes and a defining characteristic of obesity and its associated conditions, emerges as a mechanistic pathway potentially implicated in cancer pathophysiology. This presents an appealing intervention target for cancer patients. The objective of this study is to conduct a systematic review, examining the scientific evidence regarding the impact of physical activity on modifying insulin resistance in individuals with cancer.

METHODS

The selection criteria were specific: only randomized controlled clinical trials published in the last 13 years and written in English or Spanish were included. The databases utilized for the search included PubMed, Scopus, Cochrane Library, EBSCO, and WEB OF SCIENCE. The protocol for this review was duly registered in the International Register of Systematic Reviews (CRD42023435002). The final search was conducted on 14 May 2023.

RESULTS

The outcomes were assessed using the tool proposed by the Cochrane Handbook to evaluate the risk of bias in the included studies. Among the 12 studies incorporated, 8 demonstrated a low risk of bias, two had an unclear risk of bias, and the remaining two showed a high risk of bias. The variety of exercise types used across all studies was extensive, making definitive conclusions challenging. Physical activity was linked to enhanced insulin sensitivity in seven studies, while five studies showed no significant changes in insulin resistance between the intervention and control groups. Importantly, none of the interventions employed in the included studies exhibited adverse effects on the study participants.

CONCLUSIONS

The role of exercise as a medicine against insulin resistance has been evidenced in many different studies, mostly related to obesity and cardiovascular diseases. Engaging in physical activity could be a healthy option to combat the effects of insulin resistance in cancer patients, although evidence is weak and limited, according to the results of our systemic review. We further found that literature is lacking at the level of optimal doses, timing, and type of exercise. More studies are needed with more defined PA programs in type and length.

Effect of a lifestyle intervention program's on breast cancer survivors' cardiometabolic health: Two-year follow-up

The purpose of this study is to assess the cardiometabolic responses of a lifestyle intervention (LI) conducted at home among breast cancer (BC) survivors during the two years of COVID-19 pandemic. A 3-month LI focused on diet and exercise was performed on thirty BC survivors (women; stages 0-II; non-metastatic; aged 53.6 ± 7.6 years; non-physically active) with a risk factor related to metabolic/endocrine diseases. Anthropometrics, cardiorespiratory fitness (V ˙ O2max), physical activity level (PAL), adherence to the Mediterranean diet (MeDiet modified questionnaire), and several biomarkers (i.e., glycemia, insulin, insulin resistance [HOMA-IR] index, triglycerides, high- [HDL] and low- [LDL] density lipoproteins, total cholesterol, progesterone, testosterone, and hs-troponin) were evaluated before and 3-, 6-, 12-, and 24-month after the LI. Beneficial effects of the LI were observed on several variables (i.e., body mass index, waist circumference, MeDiet, PAL, V ˙ O2max, glycemia, insulin, HOMA-IR index, LDL, total cholesterol, triglycerides, testosterone) after 3-month. The significant effect on Mediterranean diet adherence and V ˙ O2max persisted up to the 24-month follow-up. Decreases in HOMA-IR index and triglycerides were observed up to 12-month, however did not persist afterward. This study provides evidence on the positive association between LI and cardiometabolic health in BC survivors.

Insulin resistance and weight gain in women treated for early stage breast cancer

PURPOSE

Both weight gain and insulin resistance have been associated with poorer prognosis in women receiving adjuvant therapy for early stage breast cancer, however, interactions between weight gain and insulin resistance have not been explored longitudinally throughout the breast cancer treatment continuum.

METHODS

One hundred non-diabetic women with early stage breast cancer receiving adjuvant chemotherapy and /or hormonal therapy were enrolled in this prospective, observational study. Metrics of weight, body composition (BMI, waist/hip circumference ratio (WHR)), and cardiometabolic health (fasting insulin, glucose and triglycerides) were obtained prior to adjuvant therapy (baseline) and repeated 6, 12, and 24 months post-diagnosis. Insulin resistance was calculated using the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR).

RESULTS

Complete data were available for 95 participants. Compared to baseline, body weight was significantly higher at the 12-month time-point (75.3 ± 15.7 vs. 76.2 ± 16.7, p = 0.03), however there was no difference in waist circumference (p = 0.96) or WHR (p = 0.52). HOMA-IR tended to increase 6 months after diagnosis (2.36 ± 2.17 vs. 2.70 ± 2.83, p = 0.06), largely driven by adverse responses in patients treated with chemotherapy (mean change + 0.53 (chemotherapy) vs - 0.64 (no chemotherapy), p = 0.005). Despite 12-month weight gain, the 6-month increase in HOMA-IR was fully abrogated 12 months after diagnosis.

CONCLUSION

Breast cancer patients experience small but significant weight gain in the year following diagnosis, and those who receive chemotherapy experience significant short-term metabolic impairments suggestive of insulin resistance. While the acute insulin resistance appears to attenuate over time, the long-term ramifications are unclear and may help explain weight gain in this population.

WISER Survivor Trial: Combined Effect of Exercise and Weight Loss Interventions on Insulin and Insulin Resistance in Breast Cancer Survivors

Obesity-associated breast cancer recurrence is mechanistically linked with elevated insulin levels and insulin resistance. Exercise and weight loss are associated with decreased breast cancer recurrence, which may be mediated through reduced insulin levels and improved insulin sensitivity. This is a secondary analysis of the WISER Survivor clinical trial examining the relative effect of exercise, weight loss and combined exercise and weight loss interventions on insulin and insulin resistance. The weight loss and combined intervention groups showed significant reductions in levels of: insulin, C-peptide, homeostatic model assessment 2 (HOMA2) insulin resistance (IR), and HOMA2 beta-cell function (β) compared to the control group. Independent of intervention group, weight loss of ≥10% was associated with decreased levels of insulin, C-peptide, and HOMA2-IR compared to 0–5% weight loss. Further, the combination of exercise and weight loss was particularly important for breast cancer survivors with clinically abnormal levels of C-peptide.

Exercise-A Panacea of Metabolic Dysregulation in Cancer: Physiological and Molecular Insights

Metabolic dysfunction is a comorbidity of many types of cancers. Disruption of glucose metabolism is of concern, as it is associated with higher cancer recurrence rates and reduced survival. Current evidence suggests many health benefits from exercise during and after cancer treatment, yet only a limited number of studies have addressed the effect of exercise on cancer-associated disruption of metabolism. In this review, we draw on studies in cells, rodents, and humans to describe the metabolic dysfunctions observed in cancer and the tissues involved. We discuss how the known effects of acute exercise and exercise training observed in healthy subjects could have a positive outcome on mechanisms in people with cancer, namely: insulin resistance, hyperlipidemia, mitochondrial dysfunction, inflammation, and cachexia. Finally, we compile the current limited knowledge of how exercise corrects metabolic control in cancer and identify unanswered questions for future research.