Letter to the Editor on: "The Effects of Physical Exercise on Tumor Vasculature: Systematic Review and Meta-Analysis."

Dear Editor,We read with interest the recent article "The Effects of Physical Exercise on Tumor Vasculature: Systematic Review and Meta-analysis" 1 and after careful appraisal and consideration we feel that some aspects of the data and analysis warrant further review. The study reported some promising results, namely that both chronic and acute exercise appear to improve intratumoral vascularisation in animal models. This is an important finding given increased vascularisation through tumor modulation may have the potential to improve chemotherapy delivery and efficacy 2. However, after conducting further investigations, we query several details in the data extraction and analysis decision-making that we believe impact the conclusions of this article.

Metabolic and behavioural effects in offspring exposed to maternal sucrose consumption: a systematic review and meta-analysis of data from rodent models.

Consumption of sugar-sweetened beverages (SSBs) during pregnancy has been associated with childhood obesity. Research in which rodent dams have been given high-fat/high-sugar diets has consistently found metabolic alterations in their offspring. However, what remains unclear is the potential impact on the developing fetus of giving sugar in isolation at concentrations similar to SSBs to the mothers. Therefore, we conducted a systematic review and meta-analysis (Protocol No: 127115 on Prospero) to identify potential relationships between maternal sucrose consumption and metabolic outcomes in offspring of rodent (rat or mouse) models. We analysed studies that provided rodent mothers dams with access to sucrose solutions (8-20% w/v) prior to conception, during pregnancy and/or lactation and that reported offspring outcomes of body weight (BW), body composition and glycaemic control. Following a systematic search of four databases (PubMed, EMBASE, Web of Science and Scopus) performed on 15 January 2019, maternal and offspring data from 15 papers were identified for inclusion. Only rat studies were identified. Meta-analyses were performed on standardised mean differences for maternal and offspring BW and fasting glucose levels, with subgroup analyses of strain, sucrose concentration, exposure period and sex of offspring. A bias towards the inclusion of only data from male offspring was identified and this limited interpretation of potential sexually dimorphic outcomes. Maternal sucrose exposure was associated with an increased risk of obesity and poor glucose disposal in adult and aged offspring.

Metabolic and behavioural effects of prenatal exposure to non-nutritive sweeteners: A systematic review and meta-analysis of rodent models.

Little is known about possible effects of maternal non-nutritive sweetener (NNS) consumption on the metabolic health of a child. Animal models of maternal NNS consumption during pregnancy or weaning have yielded widely varying results, and there appears to be no clear consensus on the consequences for offspring body weight, glycaemic control or sweet preference choices. Moreover, heterogeneity in study design has hampered a clear focus for future research relevant to human health. In an effort to bring clarity, we have conducted a systematic review and meta-analysis (protocol no: CRD42018109509) in animal models (rat or mouse) of maternal NNS feeding (compared to water or basal diet) during pre-gestation, pregnancy or lactation. Four databases were searched from inception to 15th September 2018: PubMed, EMBASE, SCOPUS and Web of Science. We present maternal and offspring data from 24 included studies, which have been quantitatively analysed after study quality assessment, to identify relationships between maternal diet and offspring body weight (BW), feeding behaviour and glycaemic control. In 11 data sets, exposure to NNS reduced maternal BW during pregnancy, with no effect on litter outcomes. Meta-analyses on offspring BW during weaning (1123 offspring) and adulthood (646 offspring) identified small decreases in BW for both sexes. Subgroup analyses revealed reductions in BW of rat, but not mouse models. High dosage appears to be a potential factor for reduced palatability that could influence BW results; however, a lack of reported data limited our ability to confirm. Despite this, and the fact many papers were predisposed to bias, the balance of evidence suggests a maternal NNS diet during pregnancy or lactation did not increase the body weight in offspring.