In isolated liver and parotid tissue samples, D-mannoheptulose blocks the first step of glucose metabolism, mostly non-competitively in liver and competitively in parotid.
See the scientific wording
In isolated liver and parotid tissue homogenates, D-mannoheptulose inhibits D-glucose phosphorylation in a mixed manner, predominantly non-competitive inhibition in liver tissue and competitive inhibition in parotid tissue.
Mixed evidence
Observational5 of 7 parts have evidence behind them.
Mixed evidence
5 of 7 parts have evidence behind them.
Parts of this claim
D-mannoheptulose inhibits D-glucose phosphorylation in isolated liver and parotid tissue homogenates.
Supported1 studyThe inhibition of D-glucose phosphorylation by D-mannoheptulose in isolated liver tissue homogenates is predominantly non-competitive.
Supported1 studyThe inhibition of D-glucose phosphorylation by D-mannoheptulose in isolated parotid tissue homogenates is competitive.
Supported1 studyThe inhibition of D-glucose phosphorylation by D-mannoheptulose interferes with glucokinase.
Supported1 studyThe inhibition of D-glucose phosphorylation by D-mannoheptulose interferes with hexokinase.
Supported1 studyGlucokinase initiates glucose metabolism.
Not testedNo studiesHexokinase initiates glucose metabolism.
Not testedNo studies
Evidence is judged against each part on its own, so a study that tests one part never counts as a verdict on the whole claim.
What the research says
1 study reviewedSupporting (1)
Cross-Sectional StudyIn vitro1998
The study directly measured D-glucose phosphorylation in liver and parotid homogenates in the presence of D-mannoheptulose and characterized the type of inhibition. The abstract reports a mixed inhibitory action, predominantly non-competitive in liver and competitive in parotid, which supports the claim that D-mannoheptulose interferes with glucokinase and/or hexokinase.
Contradicting (0)
No contradicting studies found yet
That doesn't mean it's settled — it just means no study has tested the opposite.
Quality-weighted scoring: we follow the GRADE framework — each study is rated High, Moderate, Low, or Very Low based on study design, methodology rigor, and risk of bias. A single high-quality RCT can outweigh several weaker observational studies.
Scores reflect study quality, not just count.
D-mannoheptulose is a sugar-like molecule that gets into liver and parotid cells and blocks the first protein that starts glucose breakdown. In liver, it blocks the protein in a way that does not compete with glucose. In parotid, it competes with glucose for the same spot on the protein. This stops glucose from being broken down.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting study
How Fit Body Science checks a claim
- 1
We isolate the claim
Health advice from videos, articles and studies is broken down into single, testable claims.
- 2
We find the research
Each claim is matched against peer-reviewed studies, with every source cited by DOI.
- 3
We grade the evidence
Studies are scored on methodology, statistical rigor, transparency and publication quality.
The fitness and health internet is full of confident claims. We check them against real research.
Every claim on this site is traced back to peer-reviewed studies, scored on methodology and reporting quality, and given a verdict you can audit yourself — sources, DOIs and all.
- Full evidence breakdown and mechanism chains
- Ask our AI anything about a claim or its studies
- Get notified when new research changes a verdict
In isolated liver and parotid tissue samples, D-mannoheptulose blocks the first step of glucose metabolism, mostly non-competitively in liver and competitively in parotid.
Mechanism
1 studyD-mannoheptulose stops the first step of glucose breakdown by blocking the protein that adds phosphate to glucose. In liver, it blocks the protein without competing with glucose; in parotid, it competes with glucose for the same spot. This stops glucose from being used for energy in those tissues.
D-mannoheptulose is a sugar-like molecule that gets into liver and parotid cells and blocks the first protein that starts glucose breakdown. In liver, it blocks the protein in a way that does not compete with glucose. In parotid, it competes with glucose for the same spot on the protein. This stops glucose from being broken down.
D-mannoheptulose binds to glucokinase and hexokinase, the enzymes that add phosphate to D-glucose, and blocks their activity.
Blocking these enzymes prevents D-glucose from being converted to glucose-6-phosphate, so glucose cannot enter glycolysis or further metabolism.
In liver tissue, the block is mainly non-competitive: D-mannoheptulose binds at a site separate from glucose and changes the enzyme shape so glucose cannot be processed efficiently. In parotid tissue, the block is mainly competitive: D-mannoheptulose occupies the glucose-binding site, so more glucose is needed to overcome the inhibition.
Less supported by current evidence, but not ruled out
In whole parotid cells, D-mannoheptulose does not get to the protein in high enough amounts because the cell's transport system does not bring enough of it inside or to the right place. So even though the molecule can block the protein in a test tube, it does not stop glucose breakdown in living parotid cells.
D-mannoheptulose blocks hexose phosphorylation in parotid homogenates by competing with D-glucose at the enzyme active site.
In intact parotid cells, transport and intracellular availability of D-mannoheptulose restrict its concentration at the enzyme site.
Because the inhibitor does not reach sufficient levels at hexokinase/glucokinase, D-glucose catabolism continues unaffected in intact parotid cells.
Evidence from Studies
Supporting (1)
Community contributions welcome
Contradicting (0)
Community contributions welcome
Score Breakdown
No multi-axis breakdown available yet. The overall Pro / Against score above is the best signal.
- No clinical evidence is available; the score reflects mechanistic plausibility only.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
Systematic Review and Meta-Analysis of In Vitro D-Mannoheptulose Inhibition of Glucose Phosphorylation
Systematic search of PubMed/Embase for in vitro studies using isolated liver and parotid tissue homogenates, with D-mannoheptulose at varying concentrations, measuring glucose phosphorylation rates and inhibition kinetics (Lineweaver-Burk plots) to classify competitive vs non-competitive inhibition.
Randomized Controlled Trial of D-Mannoheptulose on Human Glucose Metabolism
Double-blind, placebo-controlled RCT in healthy adults, randomizing to oral D-mannoheptulose or placebo, measuring hepatic glucose production, glucose tolerance, and indirect markers of glucokinase/hexokinase activity over 4-12 weeks.
Prospective Cohort Study of D-Mannoheptulose Exposure and Glucose Metabolism
Longitudinal cohort of adults with dietary or supplemental D-mannoheptulose intake, measuring fasting glucose, insulin, and incidence of dysglycemia over 5-10 years.
Enzyme Kinetics Study of D-Mannoheptulose Inhibition of Glucokinase and Hexokinase in Liver and Parotid Homogenates
In vitro assay using isolated liver and parotid tissue homogenates, incubating with varying D-glucose concentrations and fixed/varying D-mannoheptulose concentrations, measuring glucose-6-phosphate formation; Lineweaver-Burk and Dixon plots to classify inhibition modes for glucokinase and hexokinase.
Expert Opinion on D-Mannoheptulose as a Glucose Phosphorylation Inhibitor
Narrative review or expert consensus statement synthesizing existing biochemical knowledge on D-mannoheptulose and hexokinase/glucokinase inhibition.